Practice Test

Q1) The total energy E of the electron in a hydrogen atom is Show Answer

Q2) It is found experimentally that 13.6 eV energy is required to separate a hydrogen atom into a proton and an electron. The orbital radius is Show Answer

Q3) The wavelength of the second spectral lines in the Lyman series of the hydrogen spectrum is Show Answer

Q4) What is the shortest wavelength present in the Paschen series of the spectral lines ? Show Answer

Q5) A hydrogen atom initially in the ground level absorbs a photon which excites it to the n = 4 level. The wavelength of the photon is Show Answer

Q6) A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. What series of spectral lines will be emitted. Show Answer

Q7) The reaction that indicates beta-minus decay is Show Answer

Q8) The reaction that indicates beta-plus decay is Show Answer

Q9) One of the following is not used as a moderator in a nuclear reactor Show Answer

Q10) A radioactive isotope has a half-life of T years. How long will it take the activity to reduce to 3.125% ? Show Answer

Q11) When a hydrogen atom is raised from the ground state to an excited state Show Answer

Q12) According to Bohr's theory the radius of orbit described by principal quantum number n and atomic number Z is proportional to Show Answer

Q13) The ratio between kinetic energy and total energy of the electron of hydrogen atom, according to Bohr's model is Show Answer

Q14) In which of the following transitions will the wavelength be minimum ? Show Answer

Q15) The series limit wavelength of the Lyman series for hydrogen atom is give by Show Answer

Q16) The ionisation energy of a hydrogen- like atom is 9 Rydberg. The radius of first orbit of this atom, as compared to the radius of first orbit of hydrogen atom, will be Show Answer

Q17) Which of the following is true ? Show Answer

Q18) The minimum wavelength of X-rays produced by electrons accelerated by a potential difference of V volts is equal to Show Answer

Q19) During a negative beta decay Show Answer

Q20) Pick out the statement which is true Show Answer

Q21) Fusion reaction takes place at high temperature because Show Answer

Q22) Statement 1 : Ionisation energy of atomic hydrogen is greater than atomic deuterium.
Statement 2 : Ionisation energy is proportional to reduced mass
Show Answer

Q23) Statement 1 : Nuclear energy is due to difference in sum of masses of component nucleons and the nucleus.
Statement 2 : Mass of nucleus is more than the sum of masses of component nucleons.
Show Answer

Q24) What are number of nuclei of C, when number of nuclei of A and B are equal ? Show Answer

Q25) At what time rate of disintegration of A and B are equal ? Show Answer

Q26) Which of the following process represents a gamma-decay ? Show Answer

Q27) The mass defect for the nucleus of helium is 0.0303 amu. What is the binding energy per nucleon for helium in MeV ? Show Answer

Q28) The masses of neutron and proton are 1.0087 amu and 1.0073 amu respectively. If the neutrons and protons combine to form a helium nucleus ( alpha particles ) of mass 4.0015 amu, the binding energy of the helium nucleus will be ( 1 amu = 931 MeV) Show Answer

Q29) In final state : Show Answer

Q30) As the electron pimps, the ratio of its energy in the final state to initial state is Show Answer

Q31) If in nature there may not be an element for which the principal quantum number n > 4, then the total possible number of elements will be Show Answer

Q32) In the Bohr's hydrogen atom model, the radius of the stationary orbit is directly proportional to (n = principle quantum number) Show Answer

Q33) In the following atoms and moleculates for the transition from n= 2 to n = 1, the spectral line of minimum wavelength will be produced by Show Answer

Q34) The Lyman series of hydrogen spectrum lies in the region Show Answer

Q35) The size of an atom is of the order of Show Answer

Q36) Which one of the series of hydrogen spectrum is in the visible region Show Answer

Q37) Which of the following is true Show Answer

Q38) The energy required to knock out the electron in the third orbit of a hydrogen atom is equal to Show Answer

Q39) In a beryllium atom, if a0 be the radius of the first orbit, then the radius of the second orbit will be in general Show Answer

Q40) The ionization potential for second He electron is Show Answer

Q41) The energy required to remove an electron in a hydrogen atom from n=10 state is Show Answer

Q42) Every series of hydrogen spectrum has an upper and lower limit in wavelength. The spectral series which has an upper limit of wavelength equal to 18752 Ã… is Show Answer

Q43) The kinetic energy of the electron in an orbit of radius r in hydrogen atom is (e = electronic charge) Show Answer

Q44) Ionization potential of hydrogen atom is 13.6 V. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. The spectral lines emitted by hydrogen atoms according to Bohr's theory will be
Show Answer

Q45) The ratio of the energies of the hydrogen atom in its first to second excited state is Show Answer

Q46) The ionisation potential of hydrogen atom is 13.6 volt. The energy required to remove an electron in the n = 2 state of the hydrogen atom is Show Answer

Q47) The ionisation energy of 10 times ionised sodium atom is Show Answer

Q48) The radius of electron's second stationary orbit in Bohr's atom is R. The radius of the third orbit will be Show Answer

Q49) Which of the following particles are constituents of the nucleus Show Answer

Q50) The particles which can be added to the nucleus of an atom without changing its chemical properties are called Show Answer

Q51) The neutron was discovered by Show Answer

Q52) The mass number of a nucleus is Show Answer

Q53) The energy equivalent of 1 kilogram of matter is about Show Answer

Q54) Nuclear binding energy is equivalent to Show Answer

Q55) If the binding energy of the deutrium is 2.23 MeV.
The mass defect given in a.m.u. is
Show Answer

Q56) Which of the following has the mass closest in value to that of the positron Show Answer

Q57) Size of nucleus is of the order of Show Answer

Q58) For effective nuclear forces, the distance should be Show Answer

Q59) The masses of neutron and proton are 1.0087 a.m.u. and 1.0073 a.m.u. respectively. If the neutrons and protons combine to form a helium nucleus (alpha particles) of mass 4.0015 a.m.u. The binding energy of the helium nucleus will be (1 a.m.u.= 931 MeV) Show Answer

Q60) The mass defect for the nucleus of helium is 0.0303 a.m.u. What is the binding energy per nucleon for helium in MeV Show Answer

Q61) Atomic power station at Tarapore has a generating capacity of 200 MW. The energy generated in a day by this station is Show Answer

Q62) One microgram of matter converted into energy will give Show Answer

Q63) The average binding energy per nucleon in the nucleus of an atom is approximately Show Answer

Q64) Binding energy of a nucleus is Show Answer

Q65) Which of the following pairs is an isobar Show Answer

Q66) Equivalent energy of mass equal to 1 a.m.u. is Show Answer

Q67) The mass number of a nucleus is equal to the number of Show Answer

Q68) The rest energy of an electron is Show Answer

Q69) Outside a nucleus Show Answer

Q70) Nucleus of an atom whose atomic mass is 24 consists of Show Answer

Q71) The mass of a neutron is the same as that of Show Answer

Q72) The mass defect per nucleon is called Show Answer

Q73) The element used for radioactive carbon dating for more than 56000 yr is Show Answer

Q74) First Bohr radius of an atom with Z= 82 is R. Radius of its third orbit is Show Answer

Q75) Which is the correct expression for half-life Show Answer

Q76) The radius of a nucleus with atomic mass number 7 is 2fermi. Find the radius of nucleus with atomic number 189. Show Answer

Q77) In Bohr’s model of hydrogen atom, which of the following pairs of quantities are quantized? Show Answer

Q78) The ratio of minimum wavelength of Lyman and Balmer series will be Show Answer

Q79) The ionisation potential of hydrogen atom is −13.6 eV. An electron in the ground state of a hydrogen
atoms absorbs a photon of energy 12.75 eV. How many different spectral line can one expect when the
electron make a downward transition? Show Answer

Q80) Ionization potential of hydrogen atom is13.6 eV. Hydrogen atoms in the ground state are excited by
monochromatic radiation of photon energy 12.1 eV. According to Bohr’s theory, the spectral lines emitted
by hydrogen will be Show Answer

Q81) The ratio of areas of the electron orbits for the first excited state and the ground state for the hydrogen
atom is Show Answer

Q82) In Raman effect, Stokes’ lines are spectral lines having Show Answer

Q83) What is the difference of angular momenta of an electron in two consecutive orbits in hydrogen atom? Show Answer

Q84) The Kinetic energy of the electron in an orbit of radius r in hydrogen atom is (e=electronic charge) Show Answer

Q85) Let the PE of hydrogen atom in the ground state be zero. Then its total energy in the first excited state will be Show Answer

Q86) photon collides with a stationary hydrogen atom in ground state inelastically. Energy of the colliding photon is 10.2 eV. After a time interval of the order of micro second another photon collides with same hydrogen atom inelastically with an energy of 15n eV. What will be observed by the detector? Show Answer

Q87) When a hydrogen atom is bombared, the atom is excited to then n=4 state. The energy released, when the atom goes from n=4 state to the ground state is Show Answer

Q88) In the Bohr model of the hydrogen atom, let R,V and E represent the radius of the orbit, the speed of electron and the total energy of the electron respectively. Which of the following quantities is proportional to quantum number n? Show Answer

Q89) For ionising an excited hydrogen atom, the energy required (in eV) will be Show Answer

Q90) The angular momentum of electron in hydrogen atom is proportional to Show Answer

Q91) For an electron in the second orbit of Bohr’s hydrogen atom, the moment of linear momentum is Show Answer

Q92) If the shortest wavelength in the Lyman series is 911.6 â„«, the longest wavelength in the same series will be Show Answer

Q93) According to Bohr’s atomic model, the relation between principal quantum number(n) and radius of orbit(r) is Show Answer

Q94) The atomic number and the mass number of an atom remains unchanged when it emits Show Answer

Q95) The Rydberg constant R for hydrogen is Show Answer

Q96) Which of the following transition in Balmer series for hydrogen will have longest wavelength? Show Answer

Q97) Ionization potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are exicted by monochromatic radiation of photon energy 12.1 eV. The spectral lines emitted by hydrogen atom according to Bohr’s theory will be Show Answer

Q98) The ratio of the frequencies of the long wavelength limits of the Lyman and Balmer series of hydrogen is Show Answer

Q99) The ratio of kinetic energy and the total energy of the electron in the nth quantum state of Bohr’s atomic model of hydrogen atom is Show Answer

Q100) The ratio of minimum to maximum wavelength in Balmer series is Show Answer

Q101) Solar spectrum is an example for Show Answer

Q102) Assuming f to be frequency of first line in Balmer series, the frequency of the immediate next( i.e, second) line is Show Answer

Q103) The transition from the state n =4 to n=3 in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from Show Answer

Q104) An electron of charge e moves with a constant speed v along a circle of radius r, its magnetic moment will be Show Answer

Q105) The angular momentum (L) of an electron moving in a stable orbit around nucleus is Show Answer

Q106) Mercury vapour lamp gives Show Answer

Q107) The largest wavelength in the ultraviolet region of the hydrogen spectrum is 122 nm. The smallest wavelength in the infrared region of the hydrogen spectrum (to the nearest integer) is Show Answer

Q108) Excitation energy of a hydrogen like atom in its first excitation state is 40.8 eV. Energy needed to remove the electron from the ion in ground state is Show Answer

Q109) The ionisation potential of hydrogen atom is 13.6 eV. The energy required to remove an electron from the second orbit of hydrogen will be Show Answer

Q110) A neon sign does not produce Show Answer

Q111) If a is radius of first Bohr orbit in hydrogen atom, the radius of the third orbit is Show Answer

Q112) In the Bohr’s model of the hydrogen atom, the lowest orbit corresponds to Show Answer

Q113) In the spectrum of hydrogen atom, the ratio of the longest wavelength in Lyman series to the longest wavelength in the Balmer series is Show Answer

Q114) The colour of the second line of Balmer series is Show Answer

Q115) Continuous emission spectrum is produced by Show Answer

Q116) The total energy of an electron in the first excited state of hydrogen is about −3.4eV. Its kinetic energy in this state is Show Answer

Q117) What is the maximum wavelength of light emitted in Lyman series by hydrogen atom? Show Answer

Q118) When hydrogen atom is in its first excited level, its radius is how many times its ground state radius? Show Answer

Q119) If the electron in hydrogen atom jumps from the third to second orbit, the wavelength of the emitted radiation in terms of Rydberg constant R is given by Show Answer

Q120) The shortest wavelength in Lyman series is 91.2 nm. The longest wavelength of the series is Show Answer

Q121) In a hydrogen atom, the electron in a given orbit has total energy −1.5 eV. The potential energy is Show Answer

Q122) In an inelastic collision an electron excites a hydrogen atom from its ground state to a M-shell state. A second electron collides instantaneously with the excited hydrogen atom in the M-state and ionizes it.At least how much energy the second electron transfers to the atom in the M-state? Show Answer

Q123) The series limit wavelength of the Lyman series for the hydrogen atom is given by Show Answer

Q124) An electron is moving in an orbit of a hydrogen atom from which there can be a maximum of six transition. An electron is moving in an orbit of another hydrogen atom from which there can be a maximum of three transition. The ratio of the velocities of the electron in these two orbits is Show Answer

Q125) The ionization energy of hydrogen atom is 13.6eV. Following Bohr’s theory, the energy corresponding to a transition between 3rd and 4th orbit is Show Answer

Q126) For hydrogen atom electron in n th Bohr orbit, the ratio of radius of orbit to its de-Broglie wavelength is Show Answer

Q127) The energy of an electron in an excited hydrogen atom is −3.4 eV. Its angular momentum is Show Answer

Q128) The first excitation potential of a given atom is 10.2 V. Then ionisation potential must be Show Answer

Q129) The ionisation energy of 10 time ionised sodium atom is Show Answer

Q130) The spin-orbit interaction has no effect in the level of the hydrogen atom Show Answer

Q131) Pick out the unmatched pair from the following Show Answer

Q132) The wavelength of the first spectral line in the Balmer series of hydrogen atom is 6561 â„«. The wavelength of the second spectral line in the Balmer series of singly ionized helium atom is Show Answer

Q133) What is the radius of Iodine atom? (Atomic no.53, mass no.126) Show Answer

Q134) Hydrogen atom excites energy level from fundamental state to n=3. Number of spectrum lines, according to Bohr, is Show Answer

Q135) If elements with principal quantum number n>4 not allowed in nature, the number of possible elements would be Show Answer

Q136) Ionisation potential of hydrogen atom is 13.6 eV. The least energy of photon of Balmer series is Show Answer

Q137) A count rate metre shows a count of 240 per minute from a given radioactive source later the metre shows
a count rate 0f 30 min
. The half-life of the source is
Show Answer

Q138) The first excited state of hydrogen atoms is 10.2 eV above its ground state. The temperature needed to excite hydrogen atoms to first excited level, is Show Answer

Q139) In an atom, the two electrons move round the nucleus in circular orbits of radii R and 4R. The ratio of the times taken by them to complete one revolution is Show Answer

Q140) The orbital frequency of an electron in the hydrogen atom is proportional to Show Answer

Q141) Which of the following isotopes is normally fissionable Show Answer

Q142) When the wave of hydrogen atom comes from infinity into the first orbit then the value of wave number is Show Answer

Q143) Half-life of radioactive substance is 3.20 h. What is the time taken for a 75% of substance to be used?
Show Answer

Q144) In hydrogen atom, when electron jumps from second to first orbit, then energy emitted is Show Answer

Q145) The volume of a nucleus is directly proportional to Show Answer

Q146) Solar energy is mainly cause due to Show Answer

Q147) The ratio of minimum to maximum wavelength in Balmar series is Show Answer

Q148) Half life of a radioactive element is 10 days. The time during which quantity remains 1/10 of initial mass will be Show Answer

Q149) In beta decay Show Answer

Q150) The first line of Balmer series has wavelength 6563 â„«. What will be the wavelength of the first member of Lyman series? Show Answer

Q151) As the electron in Bohr orbit of hydrogen atom passes from state n=2 to n=1 , the kinetic energy K and potential energy U change as Show Answer

Q152) Which of the following lines of the H-atom spectrum belongs to the Balmer series? Show Answer

Q153) The production of band spectra is caused by Show Answer

Q154) Three photons coming from excited atomic hydrogen sample are observed, their energies are 12.1 eV, 10.2 eV and 1.9 eV. These photons must come from Show Answer

Q155) Electrons in the atom are held to the nucleus by Show Answer

Q156) The magnetic moment of the ground state of an atom whose open sub-shell is half-filled with five electrons is Show Answer

Q157) The energy of a hydrogen atom in its ground state is −13.6eV. The energy of the level corresponding to the quantum number n=5 is Show Answer

Q158) The spectral series of the hydrogen atom that lies in the visible ragion of the electromagnetic spectrum Show Answer

Q159) An electron collides with a hydrogen atom in its ground state and excites it to n=3. The energy given to hydrogen atom in this inelastic collision is(neglect the recoiling of hydrogen atom) Show Answer

Q160) The required energy to detach one electron from Balmer series of hydrogen spectrum is Show Answer

Q161) Which of the following transition gives the photon of minimum frequency? Show Answer

Q162) If series limit of Balmer series is 6400 â„«, then series limit of Paschen series will be Show Answer

Q163) The binding energy of the electron in the lowest orbit of the hydrogen atom is 13.6 eV. The energies required in eV to remove an electron from the three lowest orbits of the hydrogen atom are Show Answer

Q164) Hydrogen atoms are excited from ground state of the principal quantum number 4. Then the number of spectral lines observed will be Show Answer

Q165) The nucleus of an atom consists of Show Answer

Q166) The ratio of minimum wavelengths of Lyman and Balmer series will be Show Answer

Q167) The ratio of the energies of the hydrogen atom in its first to second excited states is Show Answer

Q168) Two energy lavels of an electron in an atom are separated by 2.3 eV. The frequency of radiation emitted when the electrons go from higher to lower level is Show Answer

Q169)
When an electron jumps from the orbit n=2 to n=4,then wavelength of the radiations absorbed will be (R is Rydberg’s constant) Show Answer

Q170) The spectrum of an oil flame is an example for Show Answer

Q171) At the time of total solar eclipse, the spectrum of solar radiation will have Show Answer

Q172) 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

Q173) Wavelength of light emitted from second orbit to first orbit in a hydrogen atom is Show Answer

Q174) If the wavelength of the first line of the balmer series of hydrogen is 6561â„«, the wavelength of the second line of the series should be Show Answer

Q175) If an electron is revolving around the hydrogen nucleus at a distance of 0.1 nm, what would be its speed? Show Answer

Q176) The acceleration of electron in the first orbit of hydrogen atom is Show Answer

Q177) The ratio of longest wavelength and the shortest wavelength observed in the fifth spectral series of emission spectrum of hydrogen is Show Answer

Q178) Of the following transition in the hydrogen atom, the one which gives an emission line of the highest frequency is Show Answer

Q179) Which of the following radiations has the least wavelength Show Answer

Q180) Whenever a hydrogen atom emits a photon in the Balmer series Show Answer

Q181) The ratio of the energies of the hydrogen atom in its first to second excited state is Show Answer

Q182) Radio carbon dating is done by estimating in specimen the Show Answer

Q183) Which of the following is suitable for the fusion process Show Answer

Q184) The ratio between Bohr radii are Show Answer

Q185) During a nuclear fusion reaction Show Answer

Q186) The graph between number of decayed atoms N′ of a radioactive element and time t is Show Answer

Q187) Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4.
Then the number of spectral lines in the emission spectra will be
Show Answer

Q188) The ratio of the longest to shortest wavelengths in Bracket series of hydrogen spectra is Show Answer

Q189) The ratio of the frequencies of the long wavelength limits of Lyman and Balmer series of hydrogen spectrum is Show Answer

Q190) It is easier to ionize hydrogen as compared to deuterium, because Show Answer

Q191) Half-life of radio-active substance is 140 days. Initially, is 16 g. Calculate the time for this substance when it reduces to 1 g Show Answer

Q192) If scattering particles are 56 for 90° angle, then at an angle 60° it will be Show Answer

Q193) 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

Q194) What fraction of a radioactive material will get disintegrated in a period of two half-lives Show Answer

Q195) The number of revolutions per second made by an electron in the first Bohr orbit of hydrogen atom is of the order of Show Answer

Q196) As mass number increases ,surface area Show Answer

Q197) Mark the correct statement Show Answer

Q198) The S.I. unit of radioactivity is Show Answer

Q199) When a proton, anti-proton annihilate ,the energy released is Show Answer

Q200) What is the ratio of wavelength of radiations emitted when an electron in hydrogen atom jumps from fourth orbit to second orbit and from third orbit to second orbit Show Answer

Q201) According to classical theory, the circular path of an electron in Rutherford atom is Show Answer

Q202) A radioactive substance contains 10000 nuclei and its half-life period is 20 days. The number of nuclei present at the end of 10 days is Show Answer

Q203) Nuclear forces are Show Answer

Q204) Number of spectral lines in hydrogen atom is Show Answer

Q205) In gamma ray emission from a nucleus Show Answer

Q206) The color of the second line of Balmer series is Show Answer

Q207) The nuclei of which of the following pairs of nuclei are isotones Show Answer

Q208) 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

Q209) 1 curie represents Show Answer

Q210) The mass number of a nucleus is equal to the number of Show Answer

Q211) Neutron is a particle, which is Show Answer

Q212) Which of the following is not conserved in nuclear reaction? Show Answer

Q213) In any Bohr orbit of the hydrogen atom, the ratio of kinetic energy to potential energy of the electron is Show Answer

Q214) The fact that photons carry energy was established by Show Answer

Q215) Carbon dating is best suited for determining the age of fossils of their age in years is of the order of Show Answer

Q216) The energy equivalent to 1 mg of matter in MeV is Show Answer

Q217) White light is passed through a dilute solution of potassium permanganate. The spectrum produced by the
emergent light is
Show Answer

Q218) Which of the following statements is true
Show Answer

Q219) Which of the following phenomena suggests the presence of electron energy levels in atoms Show Answer

Q220) Which one of the following nuclear reaction is a source of energy in the sun? Show Answer

Q221) The wavelength of the first line of Balmer series is 6563 â„«. The Rydberg constant for hydrogen is about Show Answer

Q222) The absorption transitions between the first and the fourth energy states of hydrogen atom are 3. The emission transitions between these states will be Show Answer

Q223) The fussion process is possible at high temperatures, because at higher temperatures Show Answer

Q224) In a radioactive disintegration , the ratio of initial number of atoms to the number of atoms present at an instant of time equal to its mean life is Show Answer

Q225) Cadmium rods are used in a nuclear reactor for Show Answer

Q226) Which shows radioactivity? Show Answer

Q227) Which of these is a fusion reaction Show Answer

Q228) The energy required to excite an electron from the ground state of hydrogen atom to the first excited state, is Show Answer

Q229) The spectral series of the hydrogen spectrum that lies in the ultraviolet region is the Show Answer

Q230) Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be Show Answer

Q231) Activity of a radioactive sample decreases to (1/3)rd of its original value in 3 days. Then, in 9 days its activity will become Show Answer

Q232) The half-life of radon is 3.8 days. How many radon will be left out of 1024 mg after 38 days Show Answer

Q233) Two nuclei have their mass numbers in the ratio of 1:3. The ratio of their nuclear densities would be Show Answer

Q234) Isobars are formed by Show Answer

Q235) The fraction of the initial number of radioactive nuclei which remain undecayed after half of a half-life of the radioactive sample is Show Answer

Q236) A radioactive substance has an average life of 5h. In a time of 5 h Show Answer

Q237) If the binding energy per nucleon of deutron is 1.115 MeV, its mass defect in atomic mass unit is Show Answer

Q238) Sun maintains its shining because of the Show Answer

Q239) With the increase in principal quantum number, the energy difference between the two successive energy levels Show Answer

Q240) The ratio of ionization energy of Bohr’s hydrogen atom and Bohr’s hydrogen like lithium atom is Show Answer

Q241) The ratio of the longest to shortest wavelengths in Lyman series of hydrogen spectra is Show Answer

Q242) If the speed of light were 2/3 of its present value, the energy released in a given atomic explosion will be decreased by a fraction Show Answer

Q243) Fusion reaction take place at high temperature because Show Answer

Q244) Plutonium decays with half-life of 24000 yr. If plutonium is stored for 7200 yr, the fraction of it that remains is Show Answer

Q245) The atoms of same element having different masses but same chemical properties, are called Show Answer

Q246) A freshly prepared radioactive source of half-life 2 h emits radiation of intensity which is 64 times the permissible safe level. Calculate the minimum time after which it would be possible to work safely with this source. Show Answer

Q247) In Raman effect, Stoke’s lines are spectral lines having Show Answer

Q248) Which of the following is true Show Answer

Q249) Ratio of the wavelengths of first line of Lyman series and first time of Balmer series is Show Answer

Q250) In the lowest energy level of hydrogen atom, the electron has the angular momentum Show Answer

Q251) Which one of the following is a possible nuclear reaction? Show Answer

Q252) In a radioactive decay, neither the atomic number nor the mass number of changes. Which of the following would be emitted in the decay process Show Answer

Q253) The first line of Balmer series has wavelength 6563 â„«. What will be the wavelength of the first member of Lyman series Show Answer

Q254) Which of the following is not conserved in nuclear reaction? Show Answer

Q255) The kinetic energy of an electron revolving around a nucleus will be Show Answer

Q256) The half-life of a radioactive substance is 40 years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant Show Answer

Q257) Ionization power and penetration range of radioactive radiation increases in the order Show Answer

Q258) The phenomena in which proton flips is Show Answer

Q259) One milligram of matter converted into energy will give Show Answer

Q260) Which one of the following nuclear reactions is a source of energy in the sun Show Answer

Q261) For nuclear forces to be effective, the distance should be Show Answer

Q262) If a proton and anti-proton come close to each other and annihilate, how much energy will be released Show Answer

Q263) Two lithium nuclei in a lithium vapour at room temperature do not combine to form a carbon nucleus because Show Answer

Q264) Atomic reactor is based on Show Answer

Q265) Pick out the correct statement from the following Show Answer

Q266) The change density in a nucleus varies with distance from the centre of the nucleus according to the curve in Fig. Show Answer

Q267) The ratio of the nuclear radii of elements with mass numbers 216 and 125 is Show Answer

Q268) A free neutron decays spontaneously into Show Answer

Q269) A radioactive sample at any instant has its disintegration rate 5000 disintegrations per minute. After 5 min, the rate becomes 1250 disintegration per minute. Then ,its decay constant (per minute) is Show Answer

Q270) The functions of moderators in nuclear reactor is to Show Answer

Q271) Which of the following transitions will have highest emission wavelength Show Answer

Q272) Hydrogen bomb is based on which of the following phenomenon Show Answer

Q273) When hydrogen atom is in its first excited level, its radius is …… its ground state radius Show Answer

Q274) What is the disintegration constant of radon if the number of its atoms diminishes by 18%in 24 h? Show Answer

Q275) Which of the relation is correct between time period and number of orbits while an electron is revolving in an orbit Show Answer

Q276) Boron rods in nuclear reactor are used as a Show Answer

Q277) Select the true statement from the following. Nuclear force is Show Answer

Q278) One Becquerel is defined as Show Answer

Q279) When the number of nucleons in nuclei increase, the binding energy per nucleon Show Answer

Q280) A chain reaction is continuous due to Show Answer

Q281) The ratio of longest wavelength and the shortest wavelength observed in the five spectral series of emission spectrum of hydrogen is Show Answer

Q282) The example of nuclear fusion is Show Answer

Q283) Age of a tree is determined using radio-isotope of Show Answer

Q284) The binding energy per nucleon for deuteron and helium are 1.1MeV and 7.0MeV. The energy released
when two deuterons fuse to form a helium nucleus is Show Answer

Q285) Half-life of a radio active substance A is 4 days. The probability that a nucleus will decay in two half-lives is Show Answer

Q286) In a sample of radioactive material, what fraction of the initial number of active nuclei will remain
undisintegrated after half of a half-life of the sample Show Answer

Q287) In radioactive decay process, the negatively charged emitted β− particles are Show Answer

Q288) A radioactive material decays by simultaneous emission of two particles with half-lives 1620 yr and 810 yr respectively. The time in year after which one-fourth of the material remains , is Show Answer

Q289) What is used as a moderator in a nuclear reactor? Show Answer

Q290) Mean life of neutron is about Show Answer

Q291) To explain his theory, Bohr used Show Answer

Q292) A radioactive substance has a half-life of four months. Three-fourth of the substance will decay in Show Answer

Q293) According to Bohr’s theory, the moment of momentum of an electron revolving in second orbit of
hydrogen atom will be Show Answer

Q294) 80 kg of a radioactive material reduces to 10 kg in 1 h. The decay constant of the material is Show Answer

Q295) The average binding energy per nucleon is maximum for the nucleus Show Answer

Q296) If half life of radium is 77 days. Its decay constant in day will be Show Answer

Q297) We have seen that a gamma-ray dose of 3Gy is lethal to half the people exposed to it. If the equivalent
energy were absorbed as heat, what rise in body temperature would result? Show Answer

Q298) Which one is correct about fission? Show Answer

Q299) In nuclear fission, the fission reactions proceeds with a projectile. Which of the following suits the best Show Answer

Q300) In a sample of hydrogen like atoms all of which are in ground state, a photon beam containing photons of
various energies is passed. In absorption spectrum, five dark lines, are observed. The number of bright
lines in the emission spectrum will be (assume that all transitions takes place) Show Answer

Q301) Heavy water is used as moderator in a nuclear reactor. The function of the moderator is Show Answer

Q302) A radioactive element forms its own isotope after 3 consecutive disintegrations. The particles emitted are Show Answer

Q303) Half life of radioactive element depends upon Show Answer

Q304) Consider the following statementsS1 : The nuclear force is independent of the charge of nucleons
S2 : The number of nucleons in the nucleus of an atom is equal to the number of electrons in the atom
S3 : All nuclei have masses that are less than the sum of the masses of constituent nucleons
S4 : Nucleons belong to the family of leptons while electrons are members of the family of hadrons
Choose the correct statement(s) from these Show Answer

Q305) The number of electrons, neutrons and protons in a species are equal to 10, 8 and 8 respectively. The proper symbol of the species is Show Answer

Q306) If half-life of radium is 77days,its decay constant will be Show Answer

Q307) The ratio of molecular mass of two radioactive substances is 3/2 and the ratio of their decay constants is 4/3. Then, the ratio of their initial activity per mole will be Show Answer

Q308) In half life of a radio isotope is 2 seconds and number of atoms are only 4, then after one half life remaining (without decay) atoms are probably Show Answer

Q309) Which one of the following statements about uranium is correct Show Answer

Q310) If an electron and a positron annihilate, then the energy released is Show Answer

Q311) The density of uranium is of the order of Show Answer

Q312) Radioactive substances do not emit Show Answer

Q313) Neutrino emission in β−decay was predicted theoretically by Show Answer

Q314) Most suitable element for nuclear fission is the element with atomic number near Show Answer

Q315) After 280 days, the activity of a radioactive sample is 6000 dps. The activity reduces to 3000dps after another 140 days. The initial activity of the sample(in dps) is Show Answer

Q316) The control rod in a nuclear reactor is made of Show Answer

Q317) A radioactive substance emits Show Answer

Q318) After two hours, one-sixteenth of the starting amount of a certain radioactive isotope remained undecayed. The half life of the isotope is Show Answer

Q319) An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be Show Answer

Q320) Alpha rays emitted from a radioactive substance are Show Answer

Q321) Which of the following statements are true regarding radioactivity (I) All radioactive elements decay exponentially with time (II) Half life time of a radioactive element is time required for one half of the radioactive atoms to disintegrate (III) Age of each can be determined with the help of radioactive dating (IV) Half life time of a radioactive element is 50% of its average life period Select correct answer using the codes given below Codes: Show Answer

Q322) The force acting between proton and proton inside the nucleus is Show Answer

Q323) In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life Show Answer

Q324) The de Broglie wave present in fifth Bohr orbit is Show Answer

Q325) A and B are two radioactive substances whose half-lives are 1 and 2 yr respectively. Initially 10 g of A and 1 g of B is taken. The time (approximate) after which they will have same quantity remaining is Show Answer

Q326) The ratio of the kinetic energy to the total energy of an electron in a Bohr orbit is Show Answer

Q327) Ionisation energy of an electron present in the second Bohr’s orbit of hydrogen is Show Answer

Q328) What percentage of original radioactive atoms is left after five half lives Show Answer

Q329) The mass number of a nucleus is 216. The size of an atom without changing its chemical properties are called Show Answer

Q330) A radioactive nucleus emits a beta particle. The parent and daughter nuclei are Show Answer

Q331) Hydrogen bomb is based upon Show Answer

Q332) Radius of the first orbit of the electron in a hydrogen atom is 0.53 â„«. So, the radius of the third orbit will be Show Answer

Q333) Radioactive nuclei that are injected into a patient collect at certain sites within its 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

Q334) According to the Rutherford’s atomic model, the electrons inside the atom are Show Answer

Q335) A nucleus is bombarded with a high speed neutron so that resulting nucleus is a radioactive one. This phenomenon is called Show Answer

Q336) Sun energy is due to Show Answer

Q337) Mass of the nucleons together in a heavy nucleus is Show Answer

Q338) The spectral series of the hydrogen atom that lies in the visible region of the electromagnetic spectrum Show Answer

Q339) The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is Show Answer

Q340) If a star can convert all the He nuclei completely into oxygen nuclei, the energy released per oxygen nuclei is ( Mass of the nucleus is 4.0026 amu and mass of oxygen nucleus is 15.9994 amu) Show Answer

Q341) The order of the size of nucleus and Bohr radius of an atom respectively are Show Answer

Q342) Who discovered spin quantum number Show Answer

Q343) For the stability of any nucleus Show Answer

Q344) The curve of binding energy per nucleon as a function of a atomic mass number has a sharp peak for helium nucleus. This implies that helium Show Answer

Q345) Radium has a half-life of 5 yr. The probability of decay of a radium nucleus in 10 yr is Show Answer

Q346) The ratio between total acceleration of the electron in singly ionized helium atom and hydrogen atom (both in ground state) is Show Answer

Q347) For maintaining sustained chain reaction, the following is required Show Answer

Q348) A radioactive material has a half life of 10 days. What fraction of the material would remain after 30 days Show Answer

Q349) The binding energy of an electron in the ground state of He is equal to 24.6 eV. The energy required to remove both the electrons is Show Answer

Q350) The splitting of line into groups under the effect of magnetic field is called Show Answer

Q351) Mean life of a radioactive sample is 100 s. Then its half-life(in minutes) is Show Answer

Q352) The half-life of a radioactive element is 3.8 days. The fraction left after 19 days will be Show Answer

Q353) The first member of the Paschen series in hydrogen spectrum is of wavelength 18,800 â„«. The short wavelength limit of Paschen series is Show Answer

Q354) The wavelength of yellow line of sodium is 5896â„«. Its wave number will be Show Answer

Q355) A radioactive sample at any instant has its disintegration rate 5000 disintegrations per minute. After 5 min, the rate is 1250 disintegrations per min. Then, the decay constant (per minute) is Show Answer

Q356) Nuclear fission experiments show that the neutrons split the uranium nuclei into two fragments of about same size. This process is accompanised by the emission of several Show Answer

Q357) If 10% of a radioactive material decays in 5 days, then the amount of original material left after 20 days is approximately Show Answer

Q358) The ratio of areas within the electron orbits for the first excited state to the ground state for hydrogen
atom is Show Answer

Q359) Best neutron moderator is Show Answer

Q360) Half-life of radium is 1600 yr. Its average life is: Show Answer

Q361) Ionisation potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1eV. The spectral lines emitted by hydrogen atoms according to Bohr’s theory will be Show Answer

Q362) 3.8 days is the half-life period of a sample. After how many days, the sample will become 1/8th of the original substance Show Answer

Q363) When a hydrogen atom is raised from the ground state to an excited state Show Answer

Q364) Orbital acceleration of electron is Show Answer

Q365) An ionic atom equivalent to hydrogen atom has wavelength equal to 1/4 of the wavelength of hydrogen lines. The ion will be Show Answer

Q366) Which of the following particle has similar mass to electron Show Answer

Q367) Select the wrong statement Show Answer

Q368) The principle of controlled chain reaction is used in Show Answer

Q369) The radius of an electron orbit in a hydrogen atom is of the order of Show Answer

Q370) Which of the following is a fusion reaction? Show Answer

Q371) 1 atomic mass unit is equal to Show Answer

Q372) Thermal neutrons can cause fission in Show Answer

Q373) The subatomic particles proton and neutron fall under the group of Show Answer

Q374) The half -life period of a radioactive substance is 3 days. Three fourth of substance decays in Show Answer

Q375) According to the quark model, it is possible to build all the hadrons using Show Answer

Q376) The wavelength of Lyman series is Show Answer

Q377) Which of the following statements are true regarding Bohr’s model of hydrogen atom (I) Orbiting speed of electron decreases as it shifts to discrete orbits away from the nucleus (II) Radii of allowed orbits of electron are proportional to the principal quantum number (III) Frequency with which electrons orbit around the nucleus is discrete orbits is inversely proportional to the cube of principal quantum number (IV) Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbits Select correct answer using the codes given below Show Answer

Q378) A radioactive substance of half-life 6 min is placed near a Geiger counter which is found to resister 1024 particles per minute. How many particles per minute will it register after 42 min? Show Answer

Q379) Nuclear fission was discovered by Show Answer

Q380) Li nucleus has three protons and four neutrons. Mass of lithium nucleus is 7.016005 amu. Mass of proton is 1.007277 amu and mass of neutron is 1.008665 amu. Mass defect for lithium nucleus in amu is Show Answer

Q381) The average binding energy per nucleon in the nucleus of an atom is approximately Show Answer

Q382) The Bohr model of atom Show Answer

Q383) The de-Broglie wavelength of an electron in the first Bohr orbit is Show Answer

Q384) Half-life of radioactive sample, when activity of material initially was 8 counts and after 3 h it becomes 1 count, is Show Answer

Q385) The set which represents the isotope, isobar and isotone respectively is Show Answer

Q386) Nuclear fusion is common to the pair Show Answer

Q387) An electron is Show Answer

Q388) The energy released in the explosion of an atom bomb is mainly due to Show Answer

Q389) Heavy water is Show Answer

Q390) In a mean life of a radioactive sample
Show Answer

Q391) Nuclear binding energy is equivalent to
Show Answer

Q392) The kinetic energy of electron in the first Bohr orbit of the hydrogen atom is
Show Answer

Q393) If the wavelength of the first line of the Balmer series of hydrogen is 6561 â„«, the wavelength of the second
line of the series should be Show Answer

Q394) The wavelength of light emitted from second orbit to first orbits in a hydrogen atom is Show Answer

Q395) 99% of a radioactive element will decay between Show Answer

Q396) The speed of daughter nuclei is Show Answer

Q397) After five half lives what will be the fraction of initial substance Show Answer

Q398) Antiparticle of electron is Show Answer

Q399) Heavy water is used in a nuclear reactor to Show Answer

Q400) What is the radius of iodine atom (at. no. 53, mass number 126) Show Answer

Q401) The large scale destruction, that would be caused due to the use of nuclear weapons is called Show Answer

Q402) The rate of disintegration of fixed quantity of a radioactive element can be increased by Show Answer

Q403) In the following transitions, which one has higher frequency Show Answer

Q404) Curie is a unit of Show Answer

Q405) What was the fissionable material used in bomb dropped at Nagasaki (Japan) in the year 1945 Show Answer

Q406) Which of the following atoms has the lowest ionization potential Show Answer

Q407) Two protons exert a nuclear force on each other, the distance between them is Show Answer

Q408) The most stable particle in Baryon group is Show Answer

Q409) Fission of nuclei is possible because the binding energy per nucleon in them Show Answer

Q410) According to Bohr’s model, the radius of the second orbit of helium atom is
Show Answer

Q411) Bohr’s atom model assumes
Show Answer

Q412) Which of the following is in the increasing order for penetrating power Show Answer

Q413) Consider two nuclei of the same radioactive nuclide. One of the nuclei was created in a supernova
explosion 5 billion years ago. The probability of decay during the next time is Show Answer

Q414) Which of the following transition in Balmer series for hydrogen atom will have longest wavelength Show Answer

Q415) A free neutron decays into a proton, an electron and Show Answer

Q416) In nuclear reactions, we have the conservation of Show Answer

Q417) Which of these is non-divisible Show Answer

Q418) Which one of the following statement is true, if half-life of a radioactive substance is 1 month? Show Answer

Q419) A radioactive substance has half-life of 60 min. During 3 h, the fraction of the substance that has to be decayed. will be Show Answer

Q420) Half-life is measured by Show Answer

Q421) The phenomenon of radioactivity is Show Answer

Q422) A moderator is used in nuclear reactors in order to Show Answer

Q423) If the binding energies of a deuteron and an alpha particle are 1.125MeV and 7.2MeV, respectively , then the more stable of the two is Show Answer

Q424) In a working nuclear reactor, cadmium rods (control rods) are used to Show Answer

Q425) The rad is the correct unit used to report the measurement of Show Answer

Q426) The masses of two radioactive substances are same and their half-lives are 1 yr and 2 yr respectively. The ratio of their activities after 4 yr will be Show Answer

Q427) The energy equivalent of the atomic mass unit is Show Answer

Q428) The concept of stationary orbits was proposed by Show Answer

Q429) If the series limit of Lymen series for Hydrogen atom is equal to the series limit of Balmer series for a hydrogen like atom, then atomic number of this hydrogen like atom will be Show Answer

Q430) In helium nucleus, there are Show Answer

Q431) Light energy emitted by stars is due to Show Answer

Q432) A radioactive element A decay into stable element B, initially a fresh sample of A is available. In this sample
variation in number of nuclei of B with time is shown by Show Answer

Q433) The energy equivalent to a kilogram of matter is about Show Answer

Q434) A photon creates a pair of electron positron with equal kinetic energy. Let kinetic energy of each particle is
0.29 MeV. Then what should be energy of the photon? Show Answer

Q435) Which of the following cannot be emitted by radioactive substances during their decay? Show Answer

Q436) The nuclear reactor at Kaiga is a Show Answer

Q437) The radius of nucleus is Show Answer

Q438) Which of the following is most unstable Show Answer

Q439) The waves emitted when a metal target is bombarded with high energy electrons are: Show Answer

Q440) The energy of He+ ion in its first exited state is, (The ground state energy for the hydrogen atom i -13.6eV) Show Answer

Q441) Choose the correct option from the following options given below Show Answer

Q442) The angular momentum for the electron in Bohr's orbit is L.If the electron is assumed to revolve in second orbit of hydrogen atom, then the change in angular momentum will be: Show Answer

Q443) A 12.2 eV electron beam is used to bombard gaseous hydrogen at room temperature. The number of spectral lines emitted will be Show Answer

Q444) An electron of a hydrogen like atom , having Z=4, jumps from 4th energy state to 2nd energy state. The energy released in this process, will be
(given, Rch=13.6 eV)
where, R=Rydberg constant, c=Speed of light in vacuum and h=Planck's constant Show Answer

Q445) Find the ratio of energies of photons produced by due to transition of an electron of hydrogen atom from its
(i)second permitted energy level to the first level, and
(ii) the highest permitted energy level to the first permitted level. Show Answer

Q446) The momentum of an electron revolving in nth orbit is given by (Symbols have their usual meanings). Show Answer

Q447) The ratio for the speed of the electron in the 3rd orbit of He+ to the speed of the electron in the 3rd orbit of hydrogen atom will be Show Answer

Q448) In Bohr's atomic model of hydrogen , let K, P and E are the kinetic energy, potential energy and total energy of the electron, respectively. Choose the correct option when the electron undergoes transitions to a higher level. Show Answer

Q449) The magnetic moment of an electron (e) revolving in an orbit around nucleus with an orbital angular momentum is given by Show Answer

Q450) Hydrogen atom from excited state comes to the ground state by emitting a photon of wavelength lambda.The value of principle quantum number n of the excited state will be (R=Rydberg constant) Show Answer

Q451) The wavelength of the photon emitted by a hydrogen atom when an electron makes a transition from n=2 to n=1 state is: Show Answer

Q452) According to Bohr atomic model, in which of the following transitions will the frequency be maximum? Show Answer

Q453) In a hydrogen atom, electron makes a transition from (n+1)th level to the nth level. If n>>1, the frequency of radiation emitted is proportional to: Show Answer

Q454) The energy required to ionise a hydrogen like ion in its ground state is 9 Rydberg. What is the wavelength of the radiation emitted when the electron in this ion jumps from the second excited state to the ground state? Show Answer

Q455) Consider an electron in a hydrogen atom, revolving in its second excited state (having radius 4.65 â„«). The de- Broglie wavelength of this electron is Show Answer

Q456) A hydrogen atom, initially in the ground state is excited absorbing a photon of wavelength 980 â„«. The radius of the atom in the excited state in terms of Bohr radius a0 will be.
(Take hc=12500 eV-â„«) Show Answer

Q457) In a hydrogen like atom, when an electron jumps from the M-shell to the L-shell, the wavelength of emitted radiation is lambda. If an electron jumps from N-shell to the L-shell, the wavelength of emitted radiation will be Show Answer

Q458) Consider an electron in a hydrogen atom, revolving in its second excited state (having radius 4.65 â„«). The de-Broglie wavelength of this electron is Show Answer

Q459) The energy required to remove the electron from a singly ionised helium atom is 2.2 times the energy required to remove and electron from helium atom. The total energy required to ionise the helium atom completely is Show Answer

Q460) The acceleration of an electron in the first orbit of hydrogen atom (n=1) is Show Answer

Q461) In a hydrogen like atom electron make transition from an energy level with quantum number n to another with quantum number (n-1). If n>>1, the frequency of radiation emitted is proportional to Show Answer

Q462) Hydrogen atom is excited from ground state to another state with principle quantum number equal to 4. Then, the number of spectral lines in the emission will be Show Answer

Q463) A diatomic molecule is made of two mass m1 and m2 which are separated by a distance r. If we calculate its rotational energy by applying momentum quantisation, its energy will be given by (n is an integer) Show Answer

Q464) The transition from the state n=4 to n=3 in a hydrogen like atom results in ultravoilet radiation. Infrared radiation will be obtained in the transition from Show Answer

Q465) Which of the following transitions in hydrogen atoms emit photons of highest frequency? Show Answer

Q466) If the binding energy of the electron in a hydrogen atom is 13.6 eV, the energy required to remove the electron from the first excited state of Li2+ is Show Answer

Q467) If 13.6 eV energy is required to ionise the hydrogen atom, then the energy required to remove an electron from n=2 is Show Answer

Q468) Given below are two statements, one is labelled as
Assertion (A) and the other is labelled as Reason (R).
Assertion (A)The binding energy per nucleon is practically independent of the atomic number for nuclei of mass number in the range 30 to 170.
Reason (R) Nuclear force is short ranged.
In the light of the above statements, choose the most appropriate answer from the options given below. Show Answer

Q469) The half-life of a radioactive substance is T. The time taken, for disintegrating 7/8th part of its original mass will be: Show Answer

Q470) The half-life of a radioactive nucleus is 5 yr. The fraction of the original sample that would decay in 15 yr is Show Answer

Q471) Substance A has atomic mass number 16 and half-life of 1 day. Another substance B has atomic mass number 32 and half-life of 1/2 days.
If both A and B simultaneously start undergo radioactivity at the same time with initial mass 320 g each, how many total atoms of A and B combined would be left after 2 days. Show Answer

Q472) Read the following statements,
(A) Volume of the nucleus is directly proportional to the mass number.
(B) Volume of the nucleus is independent of mass number.
(C) Density of the nucleus is directly proportional to the cube root of the mass number.
(D) Density of the nucleus is independent of the mass number.
(E) Density of the nucleus is independent of the mass number
Choose the correct option from the following options. Show Answer

Q473) Mass numbers of two nuclei are in the radio of 4:3. Their nuclear destinies will be in the ratio of Show Answer

Q474) A radioactive nucleus can decay by two different processes. Half-life for the first process is 3.0 h while it is 4.5 h for the second process. The effective half-life of the nucleus will be Show Answer

Q475) The half-life period of a radioactive substance is 60 days. The time taken for 7/8 th of its original mass to disintegrate will be: Show Answer

Q476) A radioactive sample decays 7/8 times its original quantity in 15 min. The half-life of the sample is Show Answer

Q477) What is the half-life period of a radioactive material, if its activity drops to 1/16th of its initial value after 30 yr? Show Answer

Q478) The half-life period of radioactive element X is same as the mean life time of another radioactive element X is same as the mean life time of another radioactive element Y. Initially, they have the same number of atoms.
Then Show Answer

Q479) Some nuclei of a radioactive material are undergoing radioactive decay. The time gap between the instances when a quarter of the nuclei have decayed and when half of the nuclei have decayed is given as (where, lambda is the decay constant): Show Answer

Q480) A sample of radioactive nucleus A disintegrates to another radioactive nucleus B, which in turn disintegrates to some other stable nucleus C. Plot of a graph showing the variation of number of atoms of nucleus B versus time is (Assume that t=0, there are no B atoms in the sample) Show Answer

Q481) Consider the following statements.
A.Atoms of each element emits characteristics spectrum.
B.According to Bohr's postulate, an electron in a hydrogen atom, revolves in a certain stationary orbit .
C.The density of nuclear matter depends on the size of the nucleus.
D.A free neutron is stable but a free proton decay is possible.
E.Radioactivity is an indication of the instability of nuclei.
Choose the correct answer from the options given below. Show Answer

Q482) A radioactive material decays by simultaneous emission of two particles with half-lives of 1400 yr and 700 yr, respectively. What will be the time after the which one-third of the material remains?
[Take, ln 3=1.1] Show Answer

Q483) The decay proton of neutron is: Show Answer

Q484) Calculate the time interval between 33% decay and 67% if half life of a substance is 20 min. Show Answer

Q485) A radioactive sample is undergoing alpha-decay. At any time t1, its activity is A and another time t2, the activity is A/5. What is the average life time for the sample?
Show Answer

Q486) Half lives of two radioactive nuclei A and B are 10 minutes and 20 minutes, respectively. If initially a sample has equal number of nuclei, then after 60 minutes, the ratio of decayed numbers of nuclei A and B will be: Show Answer

Q487) A radioactive nucleus A with a half-life T, decays into a nucleus B. At t=0, there is no nucleus B. After sometime t, the ratio of the number of B to that of A is 0.3. Then, t is given by: Show Answer

Q488) Half-lives of two radioactive elements A and B are 20 min and 40 min, respectively. Initially, the samples have equal number of nuclei. After 80 min, the ratio of decayed numbers of A and B nuclei will be: Show Answer

Q489) A radioactive nucleus (initial mass number A and atomic number Z) emits 3 alpha particles and 2 positrons. The ratio of number of neutrons to that of protons in the final nucleus will be: Show Answer

Q490) In gamma ray emission from a nucleus, Show Answer

Q491) A nucleus disintegrated into two nuclear parts which have their velocities in the ratio 2:1. The ratio of their nuclear sizes will be: Show Answer

Q492) A radioactive sample at any instant has its disintegration rate 5000 disintegration/min. After 5 min, the rate is 1250 disintegration/min. Then, the decay constant (per minute) is: Show Answer

Q493) Which of the following cannot be emitted by radioactive substances during their decay? Show Answer

Q494) At a specific instant, emission of radioactive compound is deflective in a magnetic field. The compound can emit
(i) electrons (ii)protons (iii) He2+ (iv) neutrons
The emission at the instant can be: Show Answer

Q495) The mass of proton, neutron and helium nucleus are respectively 1.0073 u, 1.0087 u and 4.0015 u. The binding energy of helium nucleus is: Show Answer

Q496) If a radioactive element having half life of 30 min is undergoing beta decay, the fraction of radioactive element remains undecayed after 90 min, will be: Show Answer

Q497) Nucleus A is having mass number 220 and its binding energy per nucleon is 5.6 MeV. It splits in two fragments B and C of mass number 105 and 115. The binding energy of nucleons in B and C is 6.4 MeV per nucleon. The energy Q released per fission will be: Show Answer

Q498) The speed of daughter nuclei is Show Answer

Q499) Statement I Energy is released when heavy nuclei undergo fission or light nuclei undergo fusion.
Statement II For heavy nuclei, binding energy per nucleon increase with increasing Z while for light nuclei, it decreases with increasing Z. Show Answer