Practice Test

Q1) A drop of radius one micron carries a charge of 4e. If the density of oil is 2g/cc, the electric field held required to balance its is : Show Answer

Q2) The distance between two plates of a cathode ray oscilloscope is 1 cm and potential difference between them is 1200 V. If an electron of energy 2000eV enters at right angles to the field, what will be the deflection if the plates are 1.5 cm long ? Show Answer

Q3) In a Thomson's set up for e/m, the same high tension d.c. supply provides potential to anode for acceleration and also the potential to anode for acceleration and also the positive voltage to the deflecting plate in the region of crossed fields. If the supply voltage is doubled, by what factor the magnetic field be increased to keep the electron beam undeflected ? Show Answer

Q4) In Millikan's oil drop method, an oil drop having a charge 'ne' is held stationary by applying a potential difference of 400 V between two parallel plates. If the size of the drop is doubled without changing the charge, the potential difference required to keep its stationary is : Show Answer

Q5) Doubly ionised helium atoms and hydrogen ions are accelerated through the same potential. The ratio of the final velocities of helium and of the hydrogen ions is : Show Answer

Q6) The ratio of specific charge e/m of an electron to that of a Hydrogen ion is : Show Answer

Q7) In a mass spectrograph, an ion A of mass number 24 and charge +e and an ion B of mass number 22 and charge +2e both enter the same magnetic field with the same velocity. The radius of circular path of A is 24cm, then the radius of circular path of B is : Show Answer

Q8) The mass of proton is 1837 times that of an electron. An electron and a proton are injected into a uniform electric field at right angles to the direction of the field with the same kinetic energy. Then : Show Answer

Q9) An electron and a proton are injected into a uniform electric field at right angles to the direction of the field with equal momentum. Then : Show Answer

Q10) An electron and a proton are injected into a uniform magnetic field at right angles to the direction of the field with the same momentum Then : Show Answer

Q11) An electron beam passes through a magnetic field of B tesla and electric of E volt/meter acting simultaneously and in mutually perpendicular direction. If the electron beam remains undeviated, the speed of electron beam must be : Show Answer

Q12) Cathode rays moving with same velocity v describe an approximate circular path of radius r meter in an electric field of strength x volt/ meter. If he speed of the cathode rays is doubled to 2v, the value of electric field needed so that the rays describe the same approximate circular path (volt/meter) is : Show Answer

Q13) Radiations of energies twice and five times the work function of metal are incident turn by turn. The ratio of max. velocities of photoelectrons in two cases will be : Show Answer

Q14) The maximum kinetic energy of the photo-electrons released when it is stopped by 2v of negative potential is : Show Answer

Q15) The ratio of wavelength of 10 KeV photon with that of 10 KeV electron is : Show Answer

Q16) Photoelectric work function of a metal is 4eV. What is the maximum wavelength to which the metal is photosensitive ? Show Answer

Q17) Bragg's equation will have no solution if : Show Answer

Q18) An electron and a proton are having same total energy, then de-Broglie wavelength is : Show Answer

Q19) The energy required to remove an electron in a hydrogen atom from n = 10 state is : Show Answer

Q20) Consider the spectral line resulting from the transition n = 2 to n = 1 in the atoms and ions given below, the shortest wavelength is produce by : Show Answer

Q21) When a photon of energy 7eV is made incident on a metal then the emitted electron is stopped by a stopping potential of -5.5 V. The work function of metal will be: Show Answer

Q22) The ratio of wavelength of a photon and that of an electron of same energy will be : Show Answer

Q23) A photon of wavelength 0.1 A is emitted by a helium atom. The recoil energy of the atom as a consequence of emission of photon will be : Show Answer

Q24) The uncertainty in the measurement of position of an electron of energy 1 Ke V is 1 A. The percentage uncertainty in the measurement of its momentum will be : Show Answer

Q25) In an X-rays tube, if the electrons are accelerated through 140 KV then anode current obtained is 30mA. If the whole energy of electrons is converted into heat then the rate of production of heat at anode will be : Show Answer

Q26) When ultraviolet radiation is incident upon a surface, no photo-electrons are emitted. If a second beam causes photo-electrons to be ejected, it may consist of : Show Answer

Q27) If 10% of the energy supplied to an incandescent light bulb is radiated as visible light, then the number of photons emitted by a 60W bulb per second will be : Show Answer

Q28) If the distance of 100 W lamp is increased from a photo cell, the saturation current in the photo cell varies with distance d as : Show Answer

Q29) A radio transmitter operates at a frequency of 800 kHz and a power of 10 kW. The number of photons emitted per second is : Show Answer

Q30) Which one of the following graphs represents correctly the variation of photoelectric current (i) with intensity (l) of incident radiations : Show Answer

Q31) For three different metals A,B,C photo-emission is observed one by one and maximum kinetic energy (K) versus frequency (v) of incident light graphs are plotted.Which fig. represents the curves correctly ? Show Answer

Q32) A photo cell is illuminated by a small bright source placed 1 m away. When the same source of light is placed 2 m away, the electrons emitted by the photo cathode : Show Answer

Q33) Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively successively illuminate a metal of work function 0.5 eV. The ratio of maximum speeds of the emitted electrons will be : Show Answer

Q34) The maximum kinetic energy of photo-electrons emitted from a surface when photons of energy 6 eV tall on it is 4 eV. The stopping potential in volts is : Show Answer

Q35) Photons of energy 6 eV fall on a photometal of work function 4 eV. The minimum kinetic energy of emitted photoelectrons is : Show Answer

Q36) A small photocell is placed at a distance of 4m from a photosensitive surface. When light falls on the surface the current is 5mA. If the distance of cell is decrease to 1m, the current will become : Show Answer

Q37) The velocity of the most energetic electrons emitted from a metal surface is doubled when the frequency v of incident radiation is doubled. The work frequency of the metal is : Show Answer

Q38) The energy of incident photon is 12.375 eV while the energy of scattered photon is 9.375 eV. Then the kinetic energy of recoil electron is : Show Answer

Q39) In Compton effect incident X-ray photon has energy 12.4 keV. If the energy of scattered photon is 6.4 keV, the kinetic energy of recoiled electron is : Show Answer

Q40) The ratio of momenta of an electron and an alpha particle which are accelerated from rest through a potential difference of 100 volts is : Show Answer

Q41) The mean free path of electron in a discharge tube is 15 cm. The length of tube is 10cm. The length of the Crooke's dark space is : Show Answer

Q42) In Millikan's oil drop experiment an oil drop of radius r and charge Q is held in equilibrium between the plates of a charged parallel plate capacitor, when the potential difference is V. To keep a drop of radius 2r, having a charge 2Q in equilibrium between the plates, the potential difference V required is : Show Answer

Q43) A charged oil drop is held stationary in an electric field. The space containing the drop is exposed to a radioactive source and drop moves with different terminal velocities V, 2V, 3V, 4V..... etc. It suggests : Show Answer

Q44) In an electron microscope if the potential is increased from 20kV to 80 kV, the resolving power R of the microscope will become : Show Answer

Q45) A photon recoils back after striking an electron at rest. What is the change in wavelength of the photon ? Show Answer

Q46) The voltage across the electrodes of a cathode ray gun is 500 volts. Calculate the momentum of the electrons. Show Answer

Q47) An electron beam passes through a parallel plate condenser. The electric intensity between plates is 20 V/cm, the distance between plates is 5cm and the length of the path traversed by beam as 10cm. Calculate the deflection angle of the beam. Show Answer

Q48) Electrons which have been accelerated by a potential difference of 1000 V enter co-terminus electric and magnetic fields of strengths 20 V/cm and 1G respectively as in the Thomson's experiment. Estimate speed of electrons if they move undeviated through the system. Show Answer

Q49) The deflecting plates in a Thomson's set up are 5.0 cm long and 1.5 cm apart. The plates are maintained at a potential difference of 240 V. Electrons accelerated to an energy of 2.0 keV enter from one edge of the plates midway in a direction parallel to the plates. What is the deflection at the other edge of the plates ? Show Answer

Q50) In a positive ray apparatus singly ionised and doubly ionised particles form identical parabolae when the magnetic fields are respectively 5 and 7.5 tesla. Compare the masses of the particles, assuming the electric field to be same. Show Answer

Q51) A hydrogen atom at rest in the second excited state emits photon when it jumps to the ground state. Calculate the de-Broglie wave-length of the hydrogen atom. Energy of ground state = - 13.6 eV. Show Answer

Q52) A photoelectric cell is illuminated by a small bright source of light placed at 1m. If the same source of light is placed 2 m away, the electrons emitted by the cathode : Show Answer

Q53) In a discharge tube at 0.1 mm of Hg there is a formation of : Show Answer

Q54) Light of frequency 1.5 times the threshold frequency is incident on a photo-sensitive material. If the frequency is halved and the intensity is doubled, the photoelectric current is doubled, the photoelectric current becomes : Show Answer

Q55) According to Bohr's theory, the electron in orbits have definite energy values, then according to uncertainty principle, the life time of a n excited state will be : Show Answer

Q56) The energy of a photon corresponding to the visible light of maximum wavelength is approximately : Show Answer

Q57) A particle of mass 1g is located in a box of size 2 cm. The uncertainty in the momentum of the electron will be : Show Answer

Q58) In a mass spectrograph, an ion A of mass number 24 and charge +e and an ion B of mass number 22 and charge +2e both enter the same magnetic field with the same velocity. The radius of circular path of A is 24 cm, then the radius of circular path of B is : Show Answer

Q59) When X-rays are scattered by electrons their wavelength increases. Their phenomenon is called : Show Answer

Q60) In a photoelectric cell, the current stops when the collecting, plate is one volt negative with respect to emitting metal. The maximum kinetic energy of the photoelectrons is : Show Answer

Q61) The number of complete de-Broglie wavelengths associated with the electron in nth orbit of hydrogen atom is : Show Answer

Q62) Einstein's work on the photoelectric effect provided support for the equation : Show Answer

Q63) Who indirectly determined the mass of the electron by measuring the change of the electron ? Show Answer

Q64) An oil drop carrying a charge q has a mass m kg. It is falling freely in air with terminal speed v. The electric field required to make the drop move upwards with the same speed is : Show Answer

Q65) A particle with a specific charge S is fired with a speed v towards a wall at a distance d, perpendicular to the wall. What minimum magnetic field must exist in this region for particle not to hit the wall ? Show Answer

Q66) Kinetic energy of emitted electron depends upon : Show Answer

Q67) Electron with energy 80 keV are incident on the tungsten target of an X-ray tube. K shell electrons of tungsten have -72.5 keV energy. X-rays emitted by the tube contain only : Show Answer

Q68) An ionised gas contains both positive and negative ions. If its is subjected simultaneously to an electric field along the + x direction and a magnetic field along the + z direction, then : Show Answer

Q69) Particle nature and wave nature of elector-magnetic wave and electrons be shown by : Show Answer

Q70) Intensity of X-ray depends upon number of : Show Answer

Q71) The energy of X-rays is 2keV, then frequency is : Show Answer

Q72) The de-Broglie wavelength of electron of energy 600 eV is : Show Answer

Q73) Gases begin to conduct electricity at low pressure because : Show Answer

Q74) The electric field required to keep a water drop of mass m just to remain suspended when charged with one electron is : Show Answer

Q75) The most important characteristic of electrons in the production of X-rays is : Show Answer

Q76) Which one among the following shows particle nature of light ? Show Answer

Q77) A photocell is illuminated by a source of light placed at a distance d. It distance is decreased to d/2, then no. of electron emitted by it : Show Answer

Q78) The work function of oxide coated tungsten emitter will be : Show Answer

Q79) If work function of metal is 3 eV then threshold wavelength will be : Show Answer

Q80) If particles are moving with same velocity, then maximum de-broglie wavelength for : Show Answer

Q81) When ultraviolet rays incident on metal plate then photoelectric effect does not occur, it occurs by incident of : Show Answer

Q82) Which of the following is not the property of cathode rays : Show Answer

Q83) An electron having charge e and mass m is moving in an electric field E. Its acceleration will be: Show Answer

Q84) The potential difference applied to an X-ray tube is 5 kV and the current through is 3.2 mA. Then the number of electrons striking the target per second is : Show Answer

Q85) J.J-Thomson's cathode-ray tube experiment demonstrated that : Show Answer

Q86) If an electron and a photon propagate in the form of waves having the same wavelength, it implies that they have the same : Show Answer

Q87) Characteristic X-rays are produced due to : Show Answer

Q88) Photoelectric effect shows : Show Answer

Q89) For a given kinetic energy which of the following has the smallest de-Broglie wavelength ? Show Answer

Q90) The phenomenon inverse to photoelectric effect is : Show Answer

Q91) The rest mass of a photon is : Show Answer

Q92) If the wavelength of the incident light changes from 400 nm to 30 nm, the shopping potential for photoelectrons emitted from a surface becomes approximately Show Answer

Q93) A photon of energy 4 eV is incident on a metal surface whose work function is 2eV. The minimum reverse potential to be applied for stopping the emission of electrons is : Show Answer

Q94) The magnitude of saturation photoelectric current depends upon : Show Answer

Q95) Monochromatic light incident on a metal surface emits electrons with kinetic energies from zero to 2.6 eV. What is the least energy of the incident photon if the tightly bound electron needs 4.2 eV to remove ? Show Answer

Q96) Which of the following have highest specific charge ? Show Answer

Q97) The wavelength of matter wave is independent of : Show Answer

Q98) A photo cell employs photoelectric effect to convert : Show Answer

Q99) In a discharge tube ionisation of enclosed gas is produce due to collisions between : Show Answer

Q100) In photoelectric effect, the electrons are ejected from metals if the incident light has a certain minimum : Show Answer

Q101) Flash light equipped with a new set of batteries produce bright white light. As the batteries wear out : Show Answer

Q102) Determine the value of n for which the de- Broglie wavelength corresponding to nth orbit is equal to wavelength of nth line of Lyman series. Given Z = 11. Show Answer

Q103) Stopping potential required to reduce the photoelectric current to zero : Show Answer

Q104) The photoelectric threshold frequency of a metal is v. When light of frequency 4v is incident on the metal, the max, kinetic energy of the emitted photo-electrons is : Show Answer

Q105) When light of wavelength 300 nm falls on a photoelectric emitter,photo-electrons are liberated. For another emitter, light of wavelength 600nm is sufficient for liberating photo-electrons. The ratio of the work function of two emitters is : Show Answer

Q106) Which of the following figure represents the variation of particle momentum and associated de-Broglie wavelength ? Show Answer

Q107) A photon in motion has a mass : Show Answer

Q108) The energy of a photon of light of wavelength 450 nm is : Show Answer

Q109) The slope of frequency of incident light and stopping potential for a given surface will be : Show Answer

Q110) Which of the following statement is correct ? Show Answer

Q111) An electron and photon have same de-Broglie wavelength. Then kinetic energy of electron is Show Answer

Q112) A radio-transmitter radiates power of 1kW at wavelength 198.6 m. How many photons does it emit per sec ? Show Answer

Q113) A parallel plate B is charged to 100 V while plate A is earthen, with separation of 1cm. A third metal plate C is introduced at a distance of 1/3 from A. An electron starts from plate A. What is minimum potential applied to C, So that electron will not reach B ?
______________________ B
______________________ C
______________________ A
+ Show Answer

Q114) Two parallel beam of electrons moving in the same direction, produce a mutual force : Show Answer

Q115) Wave is associated with matter, when : Show Answer

Q116) The light rays are incident on a metal surface. The light photons have an energy 1.8 eV and the work function of the metal is 1.2 eV. What amount of stopping potential is to be applied to stop the electrons from emitting ? Show Answer

Q117) Of which the specific charge is highest ? Show Answer

Q118) Cathode rays are a stream of : Show Answer

Q119) If the energy of a photon is increased by a factor of 4, its momentum : Show Answer

Q120) The phenomenon inverse of photoelectric effect is : Show Answer

Q121) A beam of electrons passes through undetected through mutually perpendicular electric and magnetic fields. If the electric is switched off and the same magnetic field is maintained, the electrons move : Show Answer

Q122) The work function of a surface of a photosensitive material is 6.2 eV. The wavelength of the incident radiation for which the stopping potential is 5 V lies in the : Show Answer

Q123) In the phenomenon of electric discharge through gases at low pressure, the coloured glow in the tube appears as a result of : Show Answer

Q124) Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9 mW. The number of photons arriving per sec on the average at a target irradiated by this beam is : Show Answer

Q125) Two positive ions, each carrying a charge q, are separated by a distance d. If F is the force of repulsion between the ions, the number of electrons missing from each ion will be (e being the charge on an electron ) Show Answer

Q126) A beam of cathode rays is subjected to crossed Electric (E) and Magnetic fields (B). The fields are adjusted such that the beam is not deflected the specific charge of the cathode rays is given by : Show Answer

Q127) Which one of the following bonds produces a solid that reflects light in visible region and whose electrical conductivity decreases with temperature and has high melting point ? Show Answer

Q128) Photoelectric emission occurs only when the incident light has more than a certain minimum : Show Answer

Q129) In the Davission and Germer experiment, the velocity of electrons emitted from the electrons gun can be increased by : Show Answer

Q130) Electron used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV then the de-Broglie wavelength associated with the electrons would : Show Answer

Q131) In photoelectric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. The corresponding stopping potential is : Show Answer

Q132) Silver has a work function of 4.7 eV. When ultraviolet light of wavelength 100 nm is incident upon it, a potential of 7.7 V is required to stop the photoelectrons from reaching the collector plate. How much potential will be required to stop photoelectrons when light of wavelength 200 nm is incident on silver ? Show Answer

Q133) In a photoelectric experiment, the stopping potential is V, when the frequency of incident radiation is f and V' when the frequency of incident radiation is 2f. The value of (V' - V) is : Show Answer

Q134) A proton, a deutron and an alpha particle are accelerated by same potential difference. Their velocity will be in the ratio: Show Answer

Q135) The mass of a proton is 1840 times that of an electron. An electron and proton of same initial kinetic energy enter normally in a uniform electric field. Show Answer

Q136) The specific charge of an electron is : Show Answer

Q137) Which of the following is (are) not deflected by electric and magnetic fields ? Show Answer

Q138) The energy of a photon of X-rays of wavelength 1A.U is : Show Answer

Q139) The de-Broglie wavelength of an electron having kinetic energy 500 eV is : Show Answer

Q140) The electron is nearly 200 times lighter than a proton. An electron and a proton are moving so that their matter wave have a wavelength of 1 A.U. The ratio of their kinetic energies is : Show Answer

Q141) The photoelectric effect supports quantum theory of light because : Show Answer

Q142) Lights of two different frequency whose photons have energies 2 eV and 2.5 eV respectively successively illuminate a metal whose work function is 0.5 eV. The ratio of the maximum speeds of the emitted electrons will be : Show Answer

Q143) A bulb of 10 W is at distance of 10 km from a man. How many photons are entering into the eye per second if the diameter of the eye is 2mm ? Show Answer

Q144) If the kinetic energy of the moving particles is E, then the de-Broglie wavelength is : Show Answer

Q145) The work function of a metal surface is 4.2 eV. The maximum wavelength which can eject electrons from this metal surface is : Show Answer

Q146) Neglecting variation of mass with energy the wavelength associated with an electron, having a kinetic energy E is proportional to : Show Answer

Q147) X-rays absorption will be maximum for sheets of : Show Answer

Q148) In a photoelectric experiment, photons of energy 5 eV are incident on a metal surface. The liberated photoelectrons are first stopped an electrode at a potential of 3.5 V. The work function of the metal surface is : Show Answer

Q149) The hardness of X-rays can be increased : Show Answer

Q150) Mosley's law related to : Show Answer

Q151) Velocity of an electron whose mass is ten times its rest mass is : Show Answer

Q152) Ratio of the specific charge of a proton to that of an electron is : Show Answer

Q153) For a spectral line of wavelength 400 A.U the energy in eV of the photon associated with it, is : Show Answer

Q154) X-rays of wavelength 1 A.U. when scattered in a Compton scattering in transverse direction, will have an increase in wavelength of : Show Answer

Q155) The shortest wavelength of X-rays emitted from an X-ray tube depends on : Show Answer

Q156) According to Bohr's theory the relation between main quantum number 'n' and radius of the orbit is : Show Answer

Q157) What is the energy of an emitted photon when the hydrogen atom changes from an energy state of n = 5 to n = 4 ? Show Answer

Q158) A hydrogen atom emits blue wavelength when the transition takes place n = 4 to n = 2. In which colour it would emit when the transition is form n = 5 to n = 2 ? Show Answer

Q159) For ionising an excited hydrogen atom the energy 'E' required in eV will be : Show Answer

Q160) The energy gap between successive energy levies in a hydrogen atom, with increasing order of 'n' : Show Answer

Q161) A spectral line resulting the transitions n = 2 to n = 1 in the atoms are given below. Which of these produces shortest wavelength ? Show Answer

Q162) The energy required to excite a hydrogen atom from n = 1 to n = 2 is 10.2 eV. What is wavelength emitted by atom when it returns to ground state ? Show Answer

Q163) The speed v of the electron in an orbit of radius r is : Show Answer

Q164) The first and the last member of the Lyman series are : Show Answer

Q165) The ionisation potential of hydrogen atom is 13.6 eV. The energy required to remove the electron from second orbit is : Show Answer

Q166) If the ionization energy for the hydrogen atom is 13.6 electron- volts, the energy required to excite it from the ground state to the next higher state is nearly : Show Answer

Q167) The ratio of K.E and total energy of the electron in hydrogen atom as per Bohr's model is : Show Answer

Q168) The ionisation potential of hydrogen is 13.6 eV. If the atom is excited by a monochromatic beam of 12.1 eV, the spectral lines emitted will be :` Show Answer

Q169) In an atom two electrons move round the nucleus in circular orbits of radii R and 4R. The ratio of the time taken by them to complete one revolution is : Show Answer

Q170) An electron revolves round the nucleus of charge Ze. In order to excite the electron from the state n = 2 to n = 3, the energy required is 47.2 eV. The value of Z is : Show Answer

Q171) Which of the following is true ? Show Answer

Q172) In which region of e.m. spectrum does the Lyman series of hydrogen lie ? Show Answer

Q173) The angular momentum of electron in nth orbit is given by : Show Answer

Q174) The energy required to remove an electron in a hydrogen atoms from n = 10 state is : Show Answer

Q175) The velocity of an electron in ground state is : Show Answer

Q176) Adsorption coefficient of X-rays for given wavelength is larger for Show Answer

Q177) The ionisation potential for H-atom is 14V. The K-level for atom with Z = 80 should therefore, be closest to : Show Answer

Q178) The ratio of the energies of hydrogen atom in its first and second excited states is : Show Answer

Q179) Doubly ionised helium atom and hydrogen ion are accelerated from rest through the same potential helium difference. The ratio of the final velocities of helium and hydrogen ion is : Show Answer

Q180) The stopping potential for the photoelectrons emitted from a metal of work function 1.7 eV is 10.4 V. Identify the energy levels in H-atom which emit this wavelength : Show Answer

Q181) The wavelength of the first line of the Lyman series for Hydrogen is same as that of second line of Balmer series for some hydrogen like atom X. what is the Z-value of X ? Show Answer

Q182) The ratio between K.E and the total energy of election of hydrogen atom accordingly to Bohr's model is : Show Answer

Q183) The speed of an electrons in the orbit of hydrogen atom in the ground state is : Show Answer

Q184) The ratio of magnetic dipole moment of an electron of charge e and mass in Bohr's orbit in hydrogen to its angular momentum is : Show Answer

Q185) The ratio of the radius of the orbit of the electron orbiting the hydrogen nucleus to that of an electron orbiting a deutrium nucleus is : Show Answer

Q186) The wavelength of the first line of the Lyman series for Hydrogen is same as that of second line of Balmer series for some hydrogen like atom X.Find the ionisation potential for X. Show Answer

Q187) Rydberg's constant R is equal to : Show Answer

Q188) The shortest wavelength emitted in Lymen series is : Show Answer

Q189) The difference in the angular momentum of the electron in the two successive orbits of hydrogen atom is : Show Answer

Q190) In an electronic transition, atom cannot emit : Show Answer

Q191) The kinetic energy and potential energy of the orbital electron in the hydrogen atom taking into consideration their signs as T and U, which of the following gives the total energy of electron ? Show Answer

Q192) When a particle and anti-particle combine the result is a : Show Answer

Q193) For a stability of nucleus the relations between N number of neutrons and Z atomic number should be as : Show Answer

Q194) When two protons attract each other : Show Answer

Q195) Which of the following particle is unstable ? Show Answer

Q196) The mass defect in a nuclear fusion is 0.03 per cent. Energy liberated in one kilogram of fusion is : Show Answer

Q197) The half-line of radon is 3.8 days. After how many days will 1/10th of a radon sample remain behind ? Show Answer

Q198) The decay constant of a radioactive element whose half life period is 1620 years is : Show Answer

Q199) Radioactive element has a half life of 10 days. How much element will be left after a period of 40 days if the original amount of element is 2gms ? Show Answer

Q200) The half-life of radioactive element depends on : Show Answer

Q201) A radioactive isotope has a half life period of 5 years. The fraction which decays in 15 years is : Show Answer

Q202) Half-time of an element is 140 days. Out of 16g, the 15g of element will decay in : Show Answer

Q203) Two radioactive substances 'X' and 'Y' initially contain equal number of atoms. 'X' has half-life of one hour and 'Y' has half of 2 hours. After 2 hours the ratio of the rate of disintegration of 'X' to that of y is : Show Answer

Q204) The mass defect in a nucleus with Z = 2 and A= 4 is 0.04 a.m.u. The B.E. per nucleon is : Show Answer

Q205) When one gm of mass is converted into energy, the energy released in kWh is : Show Answer

Q206) During a nuclear reaction, protons are destroyed producing an energy of 3724 MeV. The number of protons destroyed is : Show Answer

Q207) A freshly prepared radioactive source of half-life 2 hours emits of intensity which is 64 times the permissible safe level. The minimum time after which it is possible to work safely with this source is : Show Answer

Q208) Two radioactive substances 'X' and 'Y' have half - lives of T and 2T respectively. Samples of 'X' and 'Y' contain equal number of nuclei initially. After a time 4T,the ratio of undecayed atoms of 'X' to the undecayed atoms of 'Y' is : Show Answer

Q209) The radioactivity of an element becomes 1/64th of its original value in 60sec. The half-life period is : Show Answer

Q210) The mass of He is 4 and that of sulphur is 32.The radius of the sulphur nucleus is large than that of helium by the factor of : Show Answer

Q211) A certain radioactive element has half life period of 20 years. If we have a block with 10 g if the element, after how many years will there be just 2.5 g of the element left in the block ? Show Answer

Q212) A G.M counter used for measurement of the activity records 2400 counts/ minute at a certain instant and after an hour the count drops to 300 per minute. What is the half- life of the substance ? Show Answer

Q213) An atom can be considered as having a dense nucleus of neutrons and protons with surrounding distribution of electrons. If there are x- neutrons, y- protons and z- electrons, then what sort of relation exist between x, y and z in a small neutral atom ? Show Answer

Q214) The half life of radioactive radon is 3.8 days. The time at the end of which 1/20th of Randon sample will remain undecayed is : Show Answer

Q215) A sample contains 16 gms of radioactive material, the half life of which is 2 days. After 32 days, the amount of sample left is : Show Answer

Q216) A certain element disintegrates for an interval of time equal to its mean life. The fraction of the original amount that remains undecayed is Show Answer

Q217) What percentage of the original radioactive atom is left after 5 half lives ? Show Answer

Q218) A radio isotope has half life of 75 years. The fraction of this material that would decay in 150 years will be : Show Answer

Q219) At ordinary temperature when we pass light through a tube filled with hydrogen then in the absorption spectrum : Show Answer

Q220) When the electron has a transition from the state (n + 1) to state n, then frequency v of the emitted radiation will be proportional to : Show Answer

Q221) According to Bohr's theory of hydrogen atom, the angular momentum of electron in any orbit of hydrogen is : Show Answer

Q222) What percentage of radioactive substance is left after 5 half life periods ? Show Answer

Q223) An energy of 24.6 eV is required to remove one electron from a neutral helium atom. The energy (in eV) required to remove both the electrons from a neutral helium atom is : Show Answer

Q224) If the speed of the electron in a hydrogen atom orbit of principal quantum number n be v. Then the curve showing variation of v with n is : Show Answer

Q225) If the hydrogen atoms are excited to states with principal quantum number n, then the number of possible emission lines is : Show Answer

Q226) The difference in frequencies of series limit of Lymen series and Balmer series is equal to the frequency of the first line of the : Show Answer

Q227) A hydrogen atom in the ground state absorbs 12.09 eV of energy. The change in the orbital angular momentum of the electrons is : Show Answer

Q228) The area of the electron orbit for the ground state of hydrogen atom is A. Then what will be area of the electron orbit corresponding to the first excited state ? Show Answer

Q229) First excitation potential of an atom is E. What will be the ionisation potential ? Show Answer

Q230) In a hydrogen like atom, the energy required to excite the electron from IInd to the IIIrd orbit is 47.2 eV. What is the atomic number of the atom ? Show Answer

Q231) A gas of monoatomic hydrogen is bombarded with a stream of electrons that have been accelerated from rest through a potential difference of 12.75 volt. In the emission spectra one cannot observe the lines of : Show Answer

Q232) When the electron jumps from a level n = 4 to n = 1 level, the momentum of the recoiled hydrogen atom will be : Show Answer

Q233) If 10% of a radioactive material decay in 5 days, then amount of original material left after 20 days is approximately : Show Answer

Q234) The half life period of neutron is 13 minutes approximately. The intensity of neutron beam traveling in free space with a velocity of 30 km per sec is reduced to half when it cover a distance of : Show Answer

Q235) A radioactive element X with a half life of 2 hours decays giving a stable element Y. After a time t, the ratio of X to Y atoms is 1 : 7, then time t is : Show Answer

Q236) The radioactive nucleus of an element X decay to a stable nucleus Y. A graph of the rate of formation of Y against time t, would be looking like Show Answer

Q237) The counting rate observed from the radioactive source at t = 0 second was 1600 counts/sec and t = 8sec, it was 100 counts/sec. The counting rate per sec at t = 6sec will be : Show Answer

Q238) Over what distance in free space will the intensity of a 5 eV neutron beam be reduced by a factor one half ? (T = 12.8 min) Show Answer

Q239) When an electron jumps from the fourth orbit to the second orbit, one gets the : Show Answer

Q240) Some amount of radioactive substance (half life = 10 days) is spread inside a room and consequently the level of radiation becomes 50 times the permissible level for normal occupancy of the room. After how many days the room will be safe for occupation ? Show Answer

Q241) Nuclear force exists between : Show Answer

Q242) In the sum about 4 billion kg of matter is converted to energy each second. The power output of the sun is watt is : Show Answer

Q243) It is possible to understand nuclear fission on the basis of the : Show Answer

Q244) Atomic hydrogen has a life period of : Show Answer

Q245) Half-life of a substance is 20 minutes. What is the time between 33% decay and 67% decay ? Show Answer

Q246) The approximate value of quantum number n for the circular orbit of hydrogen 0.0001 mm in diameter is Show Answer

Q247) The isotope generally used for blood cancer is : Show Answer

Q248) When 3d orbital is complete, the new electron will enter in : Show Answer

Q249) An ionized gas contains both positive and negative ions. If it is subjected simultaneously to an electric field along the +x direction and a magnetic field along the +z direction, then : Show Answer

Q250) The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true ? Show Answer

Q251) If N denotes the concentration of a radioactive element,then the rate of change of concentration with time (t) can be written as : Show Answer

Q252) Which one among the following shows particle nature of light ? Show Answer

Q253) What is binding energy of hydrogen nucleus ? Show Answer

Q254) What determines half-life of a radioactive element ? Show Answer

Q255) Source of sun's energy is : Show Answer

Q256) Rutherford's X-ray scattering by particle concluded that : Show Answer

Q257) Which of the following is wrongly matched ? Show Answer

Q258) The half-life period of a substance is 1600 years. Then the amount of substance will become .......... of its initial value in 6400 years : Show Answer

Q259) The half life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially both of them have the same number of atoms. Then : Show Answer

Q260) Which of the following Indian got a Nobel Prize in Physics ? Show Answer

Q261) The wavelength of light emitted from second orbit to first orbit in a hydrogen atom is : Show Answer

Q262) 10 g of radioactive material of half life 15 years is kept in store for 20 years. The disintegrated material is : Show Answer

Q263) Recently some particles have been discovered travelling with more than the velocity of light, they are : Show Answer

Q264) The half life of a radioactive substance is 3.6 days. How much of 20 mg of this radioactive substance will remain after 36 days : Show Answer

Q265) The electron emitted in beta radiation originates from : Show Answer

Q266) Which of the following has highest neutron ratio ? Show Answer

Q267) In an atom bomb energy us released by : Show Answer

Q268) Which of the following are suitable for the fusion process ? Show Answer

Q269) Which one of the following is the weakest kind of bonding in solids ? Show Answer

Q270) Heavy water is used as a modulator in nuclear reactor. The function of the modulator is : Show Answer

Q271) A sample of an element is 10.38g. If half - life of element is 3.8 days then after 19 days how much quantity of element remains ? Show Answer

Q272) The solar energy is mainly caused due to: Show Answer

Q273) The volume occupied by an atom is greater than the volume of the nucleus by a factor of about : Show Answer

Q274) The mass number of a nucleus is : Show Answer

Q275) A sample radioactive element has a mass of 10g at an instant t = 0. The approximate mass of this element in the sample after two mean lives is : Show Answer

Q276) In which of the following systems will the radius of the first orbit (n = 1) be minimum ? Show Answer

Q277) For uranium nucleus, how does its mass vary with volume ? Show Answer

Q278) A laser beam is used for carrying out surgery because it : Show Answer

Q279) A radioactive substance decays to 1/16th of its initial activity in 40 days. The half - life of the radioactive substance expressed in days is : Show Answer

Q280) Nuclear fusion is possible : Show Answer

Q281) Radioactive nuclei that are injected into a patient collect at certain sites within his body, undergoing radioactive decay and emitting electromagnetic radiation. These radiations can then be recorded by a detector. This procedure provides an important diagnostic tool called : Show Answer

Q282) The percentage of mass covered to energy during nuclear reaction is : Show Answer

Q283) When an electron is emitted from a nucleus, then effect on its neutron - proton ratio will : Show Answer

Q284) Which one of the following is most fissionable ? Show Answer

Q285) The percentage of fissionable mass in uranium 235 is : Show Answer

Q286) Which of the following has the same mass as that of electron ? Show Answer

Q287) Shorter wavelength is of : Show Answer

Q288) For a given value of n, the possible number of electron is : Show Answer

Q289) The half-life time period of radium is 1600 years, its decay constant shall be : Show Answer

Q290) The half life of radium is about 1600 years. Of 100g of radium existing now, 25g will remain unchanged after : Show Answer

Q291) Natural uranium contains about : Show Answer

Q292) If the ionization potential of hydrogen atom is 13.6 eV then the ionization potential of Lithium is : Show Answer

Q293) The Bohr model of atoms : Show Answer

Q294) The energy difference between first two levels of hydrogen atom is 10.2 eV. For another element of atomic number 10 and mass number 20, this will be : Show Answer

Q295) For an electron in a hydrogen atom the frequency of photon for transition between levels 1 and 2 is v. The photon frequency for transition between levels 2 and 3 is close to : Show Answer

Q296) If R is Rydberg's constant then unit of Paschen series is : Show Answer

Q297) The energy level to which electron jumps from higher level to produce Balmer series of hydrogen atom is : Show Answer

Q298) The percentage change in the angular momentum of the electron when the transition is from 2nd to 1st orbit of hydrogen atom is : Show Answer

Q299) If L is the angular momentum of the electron in the second orbit of hydrogen atom, then the angular momentum in third orbit is : Show Answer

Q300) When hydrogen atom is raised from the ground state to an excited state the potential energy increases and K.E. Show Answer

Q301) After x half life times the fraction of amount which remains undecayed is : Show Answer

Q302) The fraction of a sample of radium that would remain after 4800 years is (take half life of radium = 1600 years) : Show Answer

Q303) The experimentally measured dissociation energy of Lil is : Show Answer

Q304) The Magnetic Resonance Imaging (MRI) is based atom on the phenomenon of : Show Answer

Q305) We wish to see inside an atom. Assuming the atom to have a diameter of 100 pm, this means that one must be able to resolve a width of say 10 pm. If an electron microscope is used, the minimum electron energy required is about : Show Answer

Q306) After 280 days, the activity of a radioactive sample is 6000 dps. The activity reduces to 3000 dps after another 140 days. The initial activity of the sample in dps is : Show Answer

Q307) A large scale destruction that would be caused due to use of nuclear weapons is known as : Show Answer

Q308) The nuclei of which one of the following pairs of nuclei are isotones ? Show Answer

Q309) In any fission process, the ratio
mass of fission products / mass of parent nucleus is : Show Answer

Q310) Fission of nuclei is possible because the binding energy per nucleon in them : Show Answer

Q311) The total energy of an electron in the first excited state of hydrogen atom is about -3.4 eV. Its kinetic energy is : Show Answer

Q312) The ground state energy of hydrogen atom is - 13.6 eV. What is the potential energy of the electron in this state ? Show Answer

Q313) A radioactive material has a half-life of 10 days. What fraction of the material would remain after 30 days ? Show Answer

Q314) If a star can convert all the He nuclei completely into oxygen nuclei, the energy released per oxygen nucleus is [Mass of He nucleus is 4.0026 a.m.u. and mass of Oxygen nucleus is 15.9994 a.m.u] : Show Answer

Q315) The radius of Ge nuclei is measured to be twice that of 9/4 Be. The no. of nucleons in Ge are : Show Answer

Q316) Which of the following is not a pair of isotopes ? Show Answer

Q317) The ionisation energy of 10 times ionised sodium atom is : Show Answer

Q318) A hydrogen atom in its ground state absorbs 10.2 eV of energy. The orbital angular momentum is increased by : Show Answer

Q319) Half lives of two radioactive substances A and B are respectively 20 minute and 40 minute. Initially the sample of A and B have equal number of nuclei. After 80 minutes, the ratio of number of A and B nuclei is : Show Answer

Q320) If half-life of a radioactive atom is 2.3 days, then its decay constant would be : Show Answer

Q321) The binding energy per nucleon is maximum in the case of : Show Answer

Q322) Minimum excitation of Bohr's first orbit is hydrogen atom is: Show Answer

Q323) If the binding energy of the deutrium is 2.23 MeV. The mass defect given in a.m.u is : Show Answer

Q324) A radio-isotope has a life of 5 years. The fraction of the atom of this material that would decay in 15 years will be : Show Answer

Q325) Average number of neutrons emitted per fission is : Show Answer

Q326) Critical mass of a fissionable material can be reduced by : Show Answer

Q327) Which of the following is most unstable ? Show Answer

Q328) Check the correctness of the following statements about Bohr model of hydrogen atom :
(i) the acceleration of the electron in n = 2 orbit is more than in n = 1 orbit.
(ii) the angular momentum of the electron in n = 2 orbit is more than in n = 1 orbit.
(iii) the K.E. of the electron in n = 2 orbit is less than in n = i orbit. Show Answer

Q329) The binding energy of the innermost electron in tungsten is 40 keV. To produce the characteristic X- rays, using a tungsten target in an X-ray tube, the potential difference V between the cathode and the anti-cathode should be : Show Answer

Q330) The rest energy of an electron is 0.511 MeV. The electron is accelerated from rest to a velocity 0.5 c. The change in its energy will be : Show Answer

Q331) When an atom undergoes an alpha decay, its : Show Answer

Q332) In hydrogen atom, the transition that emit radiation in the visible region is :
(n is the principal quantum number) Show Answer

Q333) A radioactive isotope has a half life of T years. The time after which its activity is reduced to 6.25% of its original activity is : Show Answer

Q334) The energy in sun is produces by : Show Answer

Q335) Suppose I mg of a radioactive substance is taken initially. After 2 hours it is found that 0.25 mg of the substance is left behind. The mean life of the substance is : Show Answer

Q336) Which one of the following is a natural source of gamma radiation ? Show Answer

Q337) A radioactive material has life of the one hour. Then the fraction of the material that remains without disintegration at the end of 4 hours is : Show Answer

Q338) What is the radius of 2nd Bohr orbit, given the radius of the first Bohr orbit is r. Show Answer

Q339) Mosley's law relates : Show Answer

Q340) In simple of radioactive material, what fraction of the initial number of active nuclei will remain un-distintegrated after half- life of the sample ? Show Answer

Q341) One milligram of matter is converted into energy, the energy released will be : Show Answer

Q342) Two nuclei have their mass numbers in the ratio of 1 : 3. The ratio of their nuclear densities would be : Show Answer

Q343) The ground state energy of hydrogen atom is -13.6 eV. When its electron is in the first excited state, its excitation energy is : Show Answer

Q344) The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an : Show Answer

Q345) The ionization energy of the electron in the hydrogen atom in its ground state is 13.6 eV. The atoms are excited to higher energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between : Show Answer

Q346) The wavelength of the first line of laymen series for hydrogen atom is equal to that of the second line of Balmer series for a hydrogen like ion. The atomic number Z of hydrogen like ion is : Show Answer

Q347) The half life of a radioactive isotope 'Y' is 50 years. It decays to another element 'Y' which is stable. The two elements 'X' and 'Y' were found to be in the ratio of 1 : 15 in a sample of a given rock. The age of the rock was estimated to be : Show Answer

Q348) A radioactive nucleus of mass M emits a photon of frequency v and the nucleus recoils. The recoils energy will be : Show Answer

Q349) Which one of the following is possible nuclear reaction ? Show Answer

Q350) Which of the following is the Einstein's photoelectric equation can be written as ? Show Answer

Q351) In the above question how many photons per second on an average are emitted by source ? Show Answer

Q352) What is the de Broglie wavelength associated with an electron accelerated through a potential difference of 100 volts. Show Answer

Q353) The photoelectric cut-off voltage in a certain experiment is 1.5 V. The maximum kinetic energy of photoelectrons emitted is Show Answer

Q354) Monochromatic light of wavelength 632.8 nm is produced by a He-Ne laser. The power emitted is 9.42 m W. How many photons per second on the average,arrive at a target irradiated by this beam ? Show Answer

Q355) For light bean of wavelength 632.8 nm, what is the momentum of each photon in the beam ? Show Answer

Q356) A 100 W sodium lamp radiates energy uniformly in all directions. The lamp is located at the center of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of the sodium light is 589 nm. At what rate are the electron delivered on the sphere ? Show Answer

Q357) The work function of a certain metal is 4.2 eV . Which among the wavelengths 390 nm, 440 nm, 550 nm and 760 nm will this metal give photoelectric emission ? Show Answer

Q358) An X-ray tube produces a continuous spectrum of radiation with its short wavelength end at 0.45 A. What is the maximum energy of a photon in the radiation. Show Answer

Q359) According to Einstein's photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal vs the frequency of the incident radiation gives a straight line whose slope Show Answer

Q360) Dual nature of radiation is shown by Show Answer

Q361) In a photoelectric cell, illuminated with a certain radiation, the minimum negative anode potential with respect to emitting metal required to stop the electron is 2 V. The maximum kinetic energy of photoelectron is Show Answer

Q362) The photoelectrons emitted from a surface of sodium metal are such that Show Answer

Q363) An ultraviolet light source causes the emission of photoelectrons from a zinc plate. A more intense source of the same wavelength would give
Maximum energy of electron No. of electrons / second Show Answer

Q364) The retarding potential for having zero photoelectron current Show Answer

Q365) Statement 1 : Electron microscope uses variable wavelengths of electrons for different resolving powers.
Statement 2 : As the accelerating voltage is increased, the wavelength of electron decreases Show Answer

Q366) The difference in maximum kinetic energy of photoelectrons from A and from B Show Answer

Q367) The threshold wavelength of A and B are related as : Show Answer

Q368) What is the ratio of the wavelengths of a photon and that of an electron of the same energy ? Show Answer

Q369) The de-Broglie wavelength of an electron is same as that of a photon. If the velocity of electron is 50% of the speed of light, then ratio of kinetic energy of photon to the kinetic energy of electron is Show Answer

Q370) An electron and a proton enter a magnetic field perpendicularly. Both have same kinetic energy. Which of the following is true ? Show Answer

Q371) Which of the following graphs correctly represents the variation of particle momentum with associated de - Broglie wavelength ? Show Answer

Q372) J.J.Thomson's cathode - ray tube experiment demonstrated that Show Answer

Q373) Photon is the name given to Show Answer

Q374) Statement 1 : Though light of a single frequency is incident on a metal, the energies of emitted photoelectrons are different.
Statement 2 : The energy of electrons emitted from inside the metal surface is lost in collision with the other atoms in the metal
Show Answer

Q375) Statement 1 : Photoelectric effect demonstrates the particle nature of electrons.
Statement 2 : The number of photoelectrons is proportional to the frequency of light.
Show Answer

Q376) The number of photons falling per seconds on each square metre of earth's surface directly below the sun is Show Answer

Q377) The number of photons in each cubic metre near the earth's surface is Show Answer

Q378) The number of photons emitted by the sun per second Show Answer

Q379) The phenomenon which is just opposite (reverse) to the photoelectric effect is Show Answer

Q380) When ultraviolet rays are incident on a photosensitive metal plate, photoemission is not possible. But it is possible by the incidence of Show Answer

Q381) A beam of light of certain intensity and wavelength ejects photoelectrons from a metal surface. This beam is then replaced by another beam of less intensity and smaller wavelength. As a result Show Answer

Q382) In the experimental arrangement of photoelectric effect, the metal surface is first illuminated with violet light and then with ultraviolet light and the stopping potential is determined in each case. The stopping potential will Show Answer

Q383) Which of the following pairs have linear relationships between themselves when photoelectrons are emitted from a surface? Show Answer

Q384) 10 photons each of energy 1.5 eV are made incident on a photosensitive plate whose work function is 3 eV. The number of electrons emitted from the plate will be Show Answer

Q385) When a beam of green light is incident on a surface, photo electrons are emitted. If a second beam of different frequency produces photoemission from the same surface, then it may consists of Show Answer

Q386) The time taken by a photoelectron to come out of the photosensitive surface after the photon strikes is approximately Show Answer

Q387) When the intensity of incident light increases, in a photo electric experiment, the Show Answer

Q388) The 22 cm radiowave emitted by hydrogen in interstellar space is due to the interaction called the hyperfine interaction in atomic hydrogen. What is the energy of the emitted wave? Show Answer

Q389) A radio transmitter operates at a frequency 880 KHz and a power of 10 kW. What is the number of photons emitted per second? Show Answer

Q390) There are two sources of light, each emitting radiations with a power of 100 W. One emits X-rays of wavelength 1 nm and the other visible light at 500 nm. What is the ratio of the number of photons of X-rays to the number of photons of visible light of the given wavelength? Show Answer

Q391) What is the maximum wavelength of light that will excite an electron in the valence band of diamond to the conduction band? The energy gap is 5.5 eV. Show Answer

Q392) The energy required to remove an electron from an aluminium surface is 4.2 eV. If two photons, each of energy 3.0 eV, strike an electron of aluminium, the emission of photoelectrons will Show Answer

Q393) Light of wavelengths 400 nanometer and 800 nanometer produces photoemission in two photoemitters. The ratio of the work function of two emitters is Show Answer

Q394) Ultraviolet radiation of 6.2 eV falls on a metallic surface. If the work function of the metal is 4.2 eV, then the kinetic energy of the fasted electron ejected from the surface is Show Answer

Q395) The maximum K.E. of photoelectrons emitted from a surface, when photons of energy 10 eV fall on it, is 4 eV. The stopping potential is Show Answer

Q396) When light of wavelength 3600 nm falls on a photosensitive plate, photoelectrons are emitted. However, for another photoelectric emitter, light of 6000 nm is sufficient to produce photoemission. What is the ratio of ran the work functions of the two emitters? Show Answer

Q397) Photons of energy 6 eV are incident on a metal surface, whose work function is 4 eV. The minimum K.E. of the emitted photoelectrons will be Show Answer

Q398) What is the stopping potential, when a metal surface with work function 1.2 eV is illuminated with light of energy 3 eV? Show Answer

Q399) When photons of energy h v fall on a metal plate, having a work function W, the maximum kinetic energy of the ejected photo electrons is K. What will be the maximum K.E. of the ejected photo electrons, from the same plate if the frequency of incident radiation is doubled? Show Answer

Q400) Planck's constant has the dimensions of Show Answer

Q401) Radiation of energy 6.5 eV is incident on a metal surface whose work function is 4.2 eV. What is the potential difference that should be applied to stop the fastest photoelectrons emitted by the metal surface? Show Answer

Q402) The threshold frequency for a photosensitive surface corresponds to an energy of 6.5 eV. If the stopping potential for radiations incident on this surface is 3V, then the energy of the incident radiation will be Show Answer

Q403) A photon of energy 7 eV is incident on a metal surface having the work function of 3.75 eV. What is the stopping potential? Show Answer

Q404) Photons of energy 1.5 eV and 2.5 eV are incident on a metal surface of work function 0.5 eV. What is the ratio of the maximum kinetic energy of the photoelectrons? Show Answer

Q405) In photoelectric effect, the work function of a metal is 3.7 eV. The emitted electron can be stopped by applying a potential of 1.8 V. Then Show Answer

Q406) Einstein's work on photoelectric effect gives support to Show Answer

Q407) The work function of a metal is 4 eV. What should be the wavelength of the incident radiation for the emission of photoelectrons of zero velocity? Show Answer

Q408) Experiments on photoelectric effect allow us to determine the value of Show Answer

Q409) Dimension's of planck's constant are the same as the dimensions of the product of Show Answer

Q410) Monochromatic light incident on a metal surface emits electrons with kinetic energies ranging from 0 to 2.5 eV. What is the least energy of the incident photon, if for removing the tightly bound electron from the metal surface an energy of 4.3 eV is required? Show Answer

Q411) The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately equal to Show Answer

Q412) When photons of energy 5 eV fall on a photosensitive surface, the maximum K.E. of the photoelectrons emitted from the surface is 2.5 eV. What is the stopping potential? Show Answer

Q413) When the frequency of the radiation incident on a photosensitive material is increased by 20%, the kinetic energy of the photoelectrons emitted from the surface increases from 0.5 eV to 0.8 eV. What is the work function of the surface? Show Answer

Q414) In a photoelectric experiment, a student plotted the graph of stopping potential (Vs) against the frequency of incident radiation (v). But he could not write the unit of the slope of the graph. What is the correct unit? Show Answer

Q415) When light of frequency v falls on a metal surface, the maximum velocity of the electrons emitted from the surface is v. What will be the maximum velocity of the ejected electrons, if the frequency is increased to 4v? Show Answer

Q416) A metal surface is exposed to light of wavelength 600 nm. The maximum energy of the electron is doubled when light of wavelength 400 nm is used. What is the work function of the metal in eV? [Given: hc = 1240 eVnm] Show Answer

Q417) When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is Show Answer

Q418) Silver has a work function of 4.7 eV. When ultraviolet light of wavelength 100 nm is incident on it, a potential difference of 7.7 V is required to stop the photoelectrons from reaching the collector plate. How much potential difference will be required to stop the photoelectrons when light of wavelength 200 nm is incident on it? Show Answer

Q419) A source of light is placed at a distance of 1 m from a photo cell and the cut off potential is found to be 5 V. If the source is kept at 1.5 m from the cell, then the cut off potential will be Show Answer

Q420) The work function of two photosensitive surfaces A and B are 5eV and 3eV. Which surface should be selected to prepare a photo cell which is to be used for visible light? Show Answer

Q421) A radio transmitter operates at a frequency of 300 KHz and a power of 10 KW. The number of photons emitted per second is approximately equal to Show Answer

Q422) A photocell is illuminated by a point source of light kept at a distance of 50 cm. If the source is shifted by 50 cm away from the photocell, then Show Answer

Q423) When an inert gas is filled in place of vacuum in a photo cell, then Show Answer

Q424) An image of the sun is formed by a convex lens of focal length 30 cm on the metal surface of a photoelectric cell and a photoelectric current I is produced. The lens forming the image is then replaced by another convex lens of the same diameter but of focal length 15 cm. What is the photoelectric current? Show Answer

Q425) When a point source of monochromatic light is at a distance of 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are 0.6 volt and 18 mA respectively. If the same source is placed 0.6 m away from the photoelectric cell, then Show Answer

Q426) Light from a hydrogen discharge tube is incident on the cathode of a photoelectric cell. The work function of the cathode surface is 4.2 eV. In order to reduce the photoelectric current to zero the voltage of the anode relative to the cathode must be made Show Answer

Q427) If a photon has a velocity c and frequency v and energy E then which one of the following expression represents its wave length? Show Answer

Q428) A particle which has zero rest mass and non zero energy and momentum travels with a speed Show Answer

Q429) The wavelength of the electromagnetic radiations whose photon has energy of 5eV is Show Answer

Q430) The energy of a photon corresponding to visible light of maximum wavelength is approximately Show Answer

Q431) The wavelength of electromagnetic radiation is doubled. What will happen to the energy of the photons of the new radiation? Show Answer

Q432) What is the momentum of a photon of energy 1 MeV in kg m/s? Show Answer

Q433) Photon of frequency v has a momentum associated with it. If c is the velocity of light, the momentum is Show Answer

Q434) The curve drawn between the velocity and the frequency of photons in vacuum will be a Show Answer

Q435) Choose the correct statement from the following. Show Answer

Q436) In Davisson-Germer experiment, an electron beam falls on a nickel crystal. The reflected beam consists of Show Answer

Q437) An alpha particle and a proton are accelerated in such a way that they get the same kinetic energy. What is the ratio of their de-Broglie wavelengths? Show Answer

Q438) The following particles are moving with the same velocity. Then the maximum de-Broglie wavelength will be for Show Answer

Q439) An electron and a proton are accelerated through the same potential difference. The ratio of their de Broglic wavelengths will be Show Answer

Q440) If the kinetic energy associated with a free electron is doubled, then its de Broglie wavelength changes by the factor Show Answer

Q441) An electron and a proton have the same de Broglie wavelength. Then the kinetic energy of the electron is Show Answer

Q442) The relation between the circumference of an electron orbit in a hydrogen atom and the de Broglie wavelength of the electron in the same orbit is given by Show Answer

Q443) The de Broglie wavelength of an electron revolving in the ground state orbit is Show Answer

Q444) An electron is having a kinetic energy of 50 eV. Its de Broglie wavelength is Show Answer

Q445) A potential difference of 15 KV is applied to accelerate in the electrons in an electron microscope. The de Broglie wavelength of the electron waves is Show Answer

Q446) Electrons kept in an enclosure at temperature T have a de Broglie wavelength lambda. If the temperature of the enclosure is increased, then the de Broglie wavelength of the electrons will Show Answer

Q447) What is the additional energy that should be supplied to a moving electron to reduce its de Broglie wavelength from 1 nm to 0.5 nm? Show Answer

Q448) The de Broglie wavelength of an electron in the first Bohr orbit is equal to Show Answer

Q449) If m is the mass of an electron and c is the speed of light, then the ratio of the wavelength of a photon of energy E to that of the electron of the same energy is Show Answer

Q450) If the de Broglie wavelength of a particle is decreased, what will happen to its momentum (p) and K.E. (K)? Show Answer

Q451) A Photon and an electron moving with a velocity v have the same de Broglie wavelength. Then the ratio of the kinetic energy of the electron to the kinetic energy of the photon is [c is the speed of light] Show Answer

Q452) If the radius of the first Bohr orbit is r, then the de Broglie wavelength of the electron in the 4th orbit will be Show Answer

Q453) A beam of electrons is used in Young's double slit experiment. The slit width is d. When the velocity of electron beam is decreased, then Show Answer

Q454) A photon, an electron and a uranium nucleus all have the same de Broglie wavelength. Which one has the maximum energy? Show Answer

Q455) The de Broglie wavelength of an electron moving in the n th Bohr orbit of radius r is given by Show Answer

Q456) Which one of the following figures gives the de-Broglie wave present in fifth Bohr orbit? Show Answer

Q457) When the momentum of a proton is changed by an amount the corresponding change in the de Broglie wavelength is found to be 0.25%. What was the original momentum of the proton? Show Answer

Q458) A material particle with a rest mass m is moving with the speed of light (c). What is the de Broglie wavelength associated with it? Show Answer

Q459) A particle is dropped from a height H. The de-Broglie wavelength of the particle as a function of height is proportional to Show Answer

Q460) If the kinetic energy of a particle is increased to 16 times its previous value, the percentage change in the de-Broglie wavelength of the particle is Show Answer

Q461) The anode voltage of a photocell is kept fixed. The wavelength A of the light falling on the cathode is gradually changed. The variation of the plate current (I) of the photocell with wavelength lambda is as shown in the figure Show Answer

Q462) According to Einstein's photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is correctly shown in figure Show Answer

Q463) Which one of the following graphs represents the variation of particle momentum and the associated de Broglie wavelength? Show Answer

Q464) Let p and E denote the linear momentum and energy of emitted photon respectively. If the wavelength of incident radiation is increased, then Show Answer

Q465) If the frequency of incident light falling on a photosensitive material is doubled, then the kinetic energy of the emitted photoelectron will be Show Answer

Q466) The number of photoelectrons emitted from a photosensitive surface Show Answer

Q467) On a photosensitive material, when the frequency of incident radiation is increased by 30%, the kinetic energy of the emitted photoelectrons increases from 0.4 eV to 0.9 eV. The work function of the surface is Show Answer