Practice Test

Q1) Pick out the longest wavelength from the following types of radiations Show Answer

Q2) What should be height of transmitting antenna if the T.V. telecast is to cover a radius of 128 km ? Show Answer

Q3) The displacement current flows in the dielectric of a capacitor when the potential difference across its plates Show Answer

Q4) Displacement current is continuous Show Answer

Q5) Kenneley's Heaviside layer lies between Show Answer

Q6) In an amplitude modulated wave for audio - frequency of 500 cycles/second, the appropriate carrier frequency will be Show Answer

Q7) Range of frequencies allotted for commercial FM radio broadcast is Show Answer

Q8) In AM systems, complete information is conveyed by transmitting in Show Answer

Q9) What is the minimum number of geostationary satellites required for uninterrupted global average ? Show Answer

Q10) In which frequency range, space waves are normally propagated Show Answer

Q11) Through which mode of propagation, the radio waves can be sent from one place to another. Show Answer

Q12) For television broadcasting, the frequency employed is normally Show Answer

Q13) An antenna behaves as a resonant circuit only when its length is Show Answer

Q14) The maximum electric field is Show Answer

Q15) The average energy density is Show Answer

Q16) At an instant when the magnetic field is along the y-axis, the electric field will be along Show Answer

Q17) Light is an electromagnetic wave. Its speed in vacuum is given by the expression Show Answer

Q18) If magnetic monopoles existed, then which of the following Maxwell's equations would be modified ? Show Answer

Q19) The number of wavelengths, in the visible spectrum is Show Answer

Q20) Which of the following electromagnetic radiations have the smallest wavelength ? Show Answer

Q21) An electromagnetic radiation has an energy 14.4 keV. To which region of electromagnetic spectrum does it belong ? Show Answer

Q22) The area to be covered for T.V. telecast is doubled. Then the height of transmitting antenna ( T.V. tower ) will have to be Show Answer

Q23) The frequency from 3 to 30 MHz is known as Show Answer

Q24) Which of the following represents an infrared wavelength ? Show Answer

Q25) In FM, modulation is doubled. This is possible if frequency deviation is Show Answer

Q26) Radio waves of constant amplitude can be generated with Show Answer

Q27) The process of superimposing signal frequency ( i.e. audio wave ) on the carrier wave is known as Show Answer

Q28) A step index fibre has a relative refractive index of 0.88%. What is the critical angle at the core - cladding interface ? Show Answer

Q29) Broadcasting antennas are generally Show Answer

Q30) The radiowaves of frequency 300 MHz to 3000 MHz belong to Show Answer

Q31) The electromagnetic waves of frequency 2 MHz to 30 MHz are Show Answer

Q32) The maximum range of ground or surface wave propagation depends on Show Answer

Q33) The maximum magnetic field is Show Answer

Q34) The maximum electric force on the electron is Show Answer

Q35) The maximum magnetic force on the electron is Show Answer

Q36) The curve drawn between velocity and frequency of a photon in vacuum will be Show Answer

Q37) Velocity of Electromagnetic Waves in a medium depends upon Show Answer

Q38) Clouds are contained in a layer from the earth’s surface, which is called Show Answer

Q39) Molybdenum is used as a target element for the production of X-rays because it is Show Answer

Q40) A radiation of 200 W is incident on a surface which is 60% reflecting and 40% absorbing. The total force on the surface is Show Answer

Q41) According to Maxwell’s hypothesis, changing electric field gives rise to Show Answer

Q42) The Electromagnetic theory of light failed to explain Show Answer

Q43) A layer of ionosphere does not reflect waves with frequencies greater than 10 MHz; then maximum electron density in this layer is Show Answer

Q44) X-rays are produced by jumping of Show Answer

Q45) The density of air at the top of mesosphere in comparison to that of near the earth’s surface is Show Answer

Q46) The wavelength of infrared rays is of the order of Show Answer

Q47) The speed of electromagnetic Wave in vacuum depends upon the source radiation. It Show Answer

Q48) Consider the following two statements regarding a linearly polarized plane electromagnetic wave
(i)Electric field and the magnetic field have equal average values
(ii)Electric energy and the magnetic energy have equal average values
Show Answer

Q49) The temperature variation in the region of stratosphere lies from Show Answer

Q50) Radio wave diffract around building although light waves do not. The reason is that radio waves Show Answer

Q51) The magnetic field between the plate of a capacitor where r>R is given by (where r is the distance from the axis of plates and R is the radius of each plate of capacitor) Show Answer

Q52) A radar sends the waves towards a distant object and receives the signal reflected by object. These waves are Show Answer

Q53) Which of the following rays is emitted by a human body? Show Answer

Q54) Which of the following relation is correct? Show Answer

Q55) The frequency 1057 MHz of radiation arising from two close energy levels in hydrogen belongs to Show Answer

Q56) X-ray are not used for radar purpose, because they are not Show Answer

Q57) If alpha, beta and gamma rays carry same momentum, which has the longest wavelength? Show Answer

Q58) If the earth did not have atmosphere, its surface temperature on a day time would be Show Answer

Q59) Which is having minimum wavelength? Show Answer

Q60) Which of the following shows green house effect? Show Answer

Q61) A charged particle with charge q enters a region of constant, uniform and mutually orthogonal fields E and B with a velocity v perpendicular to both E and B, and comes out without any change in magnitude or direction of v. Then Show Answer

Q62) An electromagnetic radiation has an energy of 13.2 keV. Then the radiation belongs to the region of Show Answer

Q63) Out of the following electromagnetic radiation, which has the shortest wavelength? Show Answer

Q64) The fact that radiosignals reach the earth from outside the atmosphere, was discovered accidently by Show Answer

Q65) The ozone layer of the atmosphere lies in the region called Show Answer

Q66) Maxwell in his famous equation of electromagnetism introduced the concept Show Answer

Q67) The relation between electric field vector E, the displacement vector D and the polarization vector P for a dielectric placed in electric field E is given by Show Answer

Q68) Electromagnetic Waves can be deflected by Show Answer

Q69) Electric fields induced by changing magnetic fields are Show Answer

Q70) The correct sequence of the increasing wavelength of the given radiation sources is Show Answer

Q71) Maxwell in his famous equation of electromagnetism introduced the concept of Show Answer

Q72) A lasser beam is sent to the moon and reflected back to earth by ay mirror placed on the moon by an astronaut. If the moon is 384000 km from earth, how long does it take the light to make the round trip? Show Answer

Q73) The energy of X-ray photon is 2200 eV. Its frequency would be Show Answer

Q74) According to Maxwell’s hypothesis, a changing electric field gives rise to Show Answer

Q75) The shortest wavelength of X-rays emitted from an X-rays tube depends upon Show Answer

Q76) Hydrogen atom does not emit X-rays because Show Answer

Q77) The waves which have revolutionized telecommunication in more recent time, are Show Answer

Q78) The wave of wavelength 5900 â„« emitted by any atom or molecule must have some finite total length which is known as the coherence length. For sodium light, this length is 2.4 cm. The number of oscillations in this length will be Show Answer

Q79) The magnetic field between the plates of radius 12 cm separated by distance of 4 mm of a parallel plate capacitor of capacitance 100 pF along the axis of plates having conduction current of 0.15 A is Show Answer

Q80) According to Maxwell’s equation the velocity of light in any medium is expressed as Show Answer

Q81) Height h of transmitter antenna when R is radius of earth to have range d is Show Answer

Q82) The voltage applied across an X-ray tube is nearly equal to Show Answer

Q83) An Electromagnetic Wave has Show Answer

Q84) The waves which are reflected back to the earth by ionosphere is Show Answer

Q85) In an Electromagnetic Wave, direction of propagation is in the direction of Show Answer

Q86) A point source of electromagnetic radiation has an average power output of 800 W. The maximum value of electric filed at a distance 4.0 m from the source is Show Answer

Q87) The oscillating electric and magnetic field vectors of electromagnetic wave are oriented along Show Answer

Q88) The electric field for a plane electromagnetic wave travelling in the positive z-direction is represented by which one of the following? Show Answer

Q89) Television signals reach us only through the ground waves. The range R related with the transmitter height h is in proportion to Show Answer

Q90) Solar radiation is Show Answer

Q91) Instantaneous displacement current of 1.0 A in the space between the parallel plate of 1 μF capacitor can be estabilished by changing potential difference of Show Answer

Q92) Ground waves have wavelength Show Answer

Q93) The wavelength of X-rays lies between Show Answer

Q94) Which of the following is absorbed by the ozone layer? Show Answer

Q95) The small ozone layer on top of the atmosphere is crucial for human survival because it Show Answer

Q96) The atmosphere above the height of 80 km is called Show Answer

Q97) The atmosphere between the heights of 50 km and 80 km is called Show Answer

Q98) If a free electron is placed in the path of a plane electromagnetic wave, it will start moving along Show Answer

Q99) Infrared radiation is detected by Show Answer

Q100) All components of the Electromagnetic Spectrum in vacuum have the same Show Answer

Q101) A. The wavelength of microwaves is greater than that of UV-rays.
B. The wavelength of IR rays is lesser than that of UV-rays.
C. The wavelength of microwaves is lesser than that of IR-rays.
D. Gamma rays have shortest wavelength in the Electromagnetic Spectrum.
Of the above statements Show Answer

Q102) The ozone layer absorbs Show Answer

Q103) Which of the following has zero average value in a plane electromagnetic wave? Show Answer

Q104) Which of the following electromagnetic waves have the longest wavelength? Show Answer

Q105) While tuning in a certain broadcast station with a receiver, we are actually Show Answer

Q106) The principle of laser action involves Show Answer

Q107) The modulation technique used for transforming digital data into analog signals are Show Answer

Q108) A laser device produces amplification in the Show Answer

Q109) Fading is the variation in the strength of a signal at a receiver due to Show Answer

Q110) Which one of the following is incorrect statement in the transmission of electromagnetic waves? Show Answer

Q111) Because of tilting which waves finally disappear Show Answer

Q112) Faintest stars are called Show Answer

Q113) A geo-synchronous satellite is Show Answer

Q114) If the area to be covered for TV telecast is doubled, then height of transmitting antenna (TV tower) will have to be Show Answer

Q115) A transmitter transmits the message in original Show Answer

Q116) In satellite communication, the communication satellite; Show Answer

Q117) The galaxy in which we live is Show Answer

Q118) In which frequencies range space waves normally propagated Show Answer

Q119) A microphone converts Show Answer

Q120) The modulation in which pulse duration varies in accordance with the modulating signal is called Show Answer

Q121) If a radio receiver amplifies all the signal frequencies equally well, it is said to have high Show Answer

Q122) Modulation is the phenomenon of Show Answer

Q123) The process of superimposing signal frequency (i.e., audio wave) on the carrier wave is known as Show Answer

Q124) The population inversion necessary for laser action used in solid state lasers is Show Answer

Q125) Major parts of a communication system are Show Answer

Q126) Numerical aperture of optical fiber is a measure of Show Answer

Q127) Primary constant of a transmission line are Show Answer

Q128) In frequency modulated wave Show Answer

Q129) Long distance short-wave radio broadcasting uses Show Answer

Q130) An antenna is a device Show Answer

Q131) The space wave propagation is utilized in Show Answer

Q132) Which of the following is correct? Show Answer

Q133) Audio signal cannot be transmitted because Show Answer

Q134) Antenna is Show Answer

Q135) In pulse modulation of analog signals, common pulse system employed are Show Answer

Q136) Which of the following is not the main characteristic of laser beam? Show Answer

Q137) A laser beam is used for carrying out surgery because it Show Answer

Q138) A receiver reconstructs the original message after propagation through the channel. Show Answer

Q139) The frequency of a FM transmitter without signal input is called Show Answer

Q140) Ozone layer above earth's atmosphere will not Show Answer

Q141) A signal emitted by an antenna from a certain point can be received at another point of the surface in the form of Show Answer

Q142) The losses in transmission lines are Show Answer

Q143) Which of the following is the disadvantage of FM over AM Show Answer

Q144) Advantage of optical fibre is Show Answer

Q145) Basically, a communication system is a Show Answer

Q146) When electromagnetic waves enter the ionised layer of ionosphere, then the relative permittivity
ie,dielectric constant dielectric constant of the ionised layer Show Answer

Q147) Laser beams are used to measure long distances because Show Answer

Q148) Basically, the product modulator is Show Answer

Q149) The phenomenon by which light travels in an optical fibres is Show Answer

Q150) The output stage of a television transmitter is most likely to be a Show Answer

Q151) Small vales of numerical aperture (NA) decrease the pulse dispersion but increase losses due to Show Answer

Q152) A modem is a Show Answer

Q153) Optical fibre works on the principle of Show Answer

Q154) Large band width for higher data rate is achieved by using Show Answer

Q155) Venus looks brighter than other stars, due to Show Answer

Q156) The SKIP ZONE in Radio Wave Transmission is that range where Show Answer

Q157) Which is more advantageous? Show Answer

Q158) Which one of the following is a full duplex transmission system? Show Answer

Q159) A laser is a coherent source because it contains Show Answer

Q160) In amplitude modulation, carrier wave frequencies are Show Answer

Q161) The population inversion in helium-neon laser is produced by Show Answer

Q162) The closed structure of co-axial cable prevents inner copper wire or core or from radiating signal power. The statement is Show Answer

Q163) Of the following which is preferred modulation scheme for digital communication Show Answer

Q164) In ruby laser, the stimulated emission is due to transition from Show Answer

Q165) A laser beam is used for locating distant objects because Show Answer

Q166) The principle used in the transmission of signal through an optical fibre is Show Answer

Q167) Which fibers are less expensive and simple to construct? Show Answer

Q168) Intelsat satellite is used for Show Answer

Q169) In the communication systems, AM is used for broadcasting because Show Answer

Q170) The special theory of relativity is based on the frame of reference which has constant? Show Answer

Q171) Through which mode of propagation, the radio waves can be sent from one place to another Show Answer

Q172) Optical fiber communication is generally preferred over general communication system because Show Answer

Q173) In space communication, the sound waves can be sent from one place to another Show Answer

Q174) In frequency modulation Show Answer

Q175) The highest frequency of radiowaves which when sent at some angle towards the ionosphere, gets reflected from that and returns to the earth is called Show Answer

Q176) The main objective of an optical source is Show Answer

Q177) The range of frequencies allotted for FM radio is Show Answer

Q178) The transmission media can be Show Answer

Q179) A communication between a fixed base station and several mobile units, located on ships or aircraft utilising two way radio communication in the VHF and UHF is of frequency band Show Answer

Q180) Point to point communication requires the use of Show Answer

Q181) What type of modulation is employed in India for radio transmission Show Answer

Q182) The layer of earth's atmosphere responsible for absorbing a large portion of ultraviolet radiations by the sun is Show Answer

Q183) Which of the following device is fully duplex Show Answer

Q184) Special theory of relativity states that Show Answer

Q185) Modulation is the process of superposing Show Answer

Q186) In which of the following remote sensing technique is not used Show Answer

Q187) The electromagnetic waves of frequency 2 MHz to 30 MHz are used Show Answer

Q188) The frequency band used in the downlink of satellite communication is Show Answer

Q189) The attenuation in optical fibre is mainly due to Show Answer

Q190) Present day communication systems are Show Answer

Q191) Flash spectrum confirms a/an Show Answer

Q192) Which of the following four alternatives is not correct? We need modulation Show Answer

Q193) For maximum power transfer to the load, impedance of the detecting device must be equal to characteristic impedance of the transmission line Show Answer

Q194) Quality of transmission depends only Show Answer

Q195) In a communication system, noise is most likely to affect the signal Show Answer

Q196) In co-axial cable the material used as spacer is Show Answer

Q197) What is the range of the characteristic impedance of a coaxial cable? Show Answer

Q198) The velocity of electromagnetic waves in a dielectric medium of constant 4 is Show Answer

Q199) Identify the incorrect statement from the following Show Answer

Q200) The velocity of a particle at which the kinetic energy is equal to its rest energy is Show Answer

Q201) The difference in the refractive index of the fiber core and fiber cladding in step-index fibers is typically Show Answer

Q202) In amplitude modulation, the bandwidth is Show Answer

Q203) Consider telecommunication through optical fibres. Which of the following statements is no true? Show Answer

Q204) Which of the following explain that all galaxies are receding from us? Show Answer

Q205) 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

Q206) An optical fiber made of glass with a core of refractive index of 1.55 and include with another glass with a refractive index of 1.51. Launching takes place from air. What is the value of critical angle for core-clad boundary? Show Answer

Q207) The modulation index of a FM signal is 0.25. If modulating frequency is 2kHz, the maximum derivative in frequency would be Show Answer

Q208) The resistance of copper wire of diameter=2 mm is of the order of Show Answer

Q209) A 1000kHz carrier wave is modulated by audio signal of frequency range 100-5000Hz. Then the width of the channel in kHz is Show Answer

Q210) Frequency range for microwaves is Show Answer

Q211) If an electromagnetic wave is transmitted to the height equal to 150 km with maximum frequency 300 kHz and critical frequency 100 kHz, the skip distance is Show Answer

Q212) The waves relevant to telecommunications are Show Answer

Q213) The maximum peak to peak voltage of an AM wire is 24 mV and the minimum peak to peak voltage is 8 mV. The modulation factor is Show Answer

Q214) The length of a half wave dipole at 30 MHz is Show Answer

Q215) In space communication, the information can be passed from one place to another at a distance of 100 km in Show Answer

Q216) A radio station has two channels. One is AM at 1020 kHz and the other FM at 89.5 Mhz For good results you will use Show Answer

Q217) A carrier is simultaneously modulated by two sine waves having modulation indices of 0.3 and 0.4. The total modulation index will be Show Answer

Q218) A transmitting antenna of height h and the receiving antenna of height 45 m are separated by a distance of 40 km for satisfactory communication in line of sight mode. Then the value of h is Show Answer

Q219) What is the minimum length of antenna required to transmit a radio signal of frequency 20 MHz? Show Answer

Q220) The glass of optical fiber has refractive index 1.55 and is clad with another glass of refractive index 1.51. When the surrounding is air, the numerical aperture will be Show Answer

Q221) Which of the following statements is wrong? Show Answer

Q222) For a body moving with relativistic speed, if the velocity is doubled, then Show Answer

Q223) In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be Show Answer

Q224) Range of frequencies allotted for commercial UHF TV broadcast is Show Answer

Q225) What fraction of the surface area of earth can be covered to establish communication by one geostationary satellite? Show Answer

Q226) A carrier frequency of 1MHz and peak value of 10V is amplitude modulated with a signal frequency of 10 kHz with peak value of 0.5 V. Then the modulation index and the side band frequencies respectively are Show Answer

Q227) When radio waves passes through ionosphere, phase difference between space current and capacitive displacement current is Show Answer

Q228) In optical communication system operating at 1200 nm, only 2% of the source frequency is available for TV transmission having a bandwidth of 5 MHz. The number of TV channels that can be transmitted is Show Answer

Q229) In satellite communication
1. The frequency used lies between 5 MHz and 10 MHz
2. The uplink and downlink frequencies are different.
3. The orbit of geostationary satellite lies in the equatorial plane at an inclination of 0°.
In the above statements
Show Answer

Q230) A 500 Hz modulating voltage fed into an FM generator produces a frequency deviation of 2.25 kHz. If amplitude of the voltage is kept constant but frequency is raised to 6 kHz then the new deviation will be Show Answer

Q231) The antenna current of an AM transmitter is 8 A when only the carrier is sent, but it increases to 8.93 A when the carrier is modulated by single sine wave. Find the percentage modulation. Show Answer

Q232) The diameter of an optical fiber is Show Answer

Q233) The characteristic impedance of a coaxial cable is of the order of Show Answer

Q234) The cladding material of optical fibre has refractive index Show Answer

Q235) Two electrons are moving in opposite direction with speeds 0.8 c and 0.4 c, where c the speed of light in vacuum. Then the relative speed is about Show Answer

Q236) According o Hubble’s law the red-shift (Z) of a receding galaxy and its distance r from earth are related as Show Answer

Q237) Which of the following frequencies will be suitable for beyond the horizon communication Show Answer

Q238) An antenna is of height 500 m. What will be its range (Radius of earth is 6400 km)? Show Answer

Q239) The antenna current of an AM broadcast transmitter modulated by 50% is 11. Find the carrier current Show Answer

Q240) What should be the maximum acceptance angle at the aircore interface of an optical fibre if n1 and n2 are the refractive indices of the core and the cladding, respectively Show Answer

Q241) A dim star of magnitude + 14.5 explodes into a nova a magnitude +2. The factor by which the brightness of the star has increased is Show Answer

Q242) The velocity of electromagnetic wave in good conductor is Show Answer

Q243) The bit rate for a signal, which has a sampling rate of 8 kHz and where 16 quantisation levels have been used is Show Answer

Q244) A broken ligament is being ‘welded’ back in place using 20 ms pulses from a 0.5 W laser operating at a wavelength of 632 nm. The number of photons in 5 pulses of laser are Show Answer

Q245) Ozone layer blocks the radiations of wavelength Show Answer

Q246) Which one of the following statements is wrong? Show Answer

Q247) A step index fibre has a relative refractive index of 0.88%. What is the critical angle at the corecladding interface Show Answer

Q248) If sky wave with frequency of 50 MHz is incident on D region at an angle of 30°, then angle of refraction is Show Answer

Q249) When the modulation percentage is 75, an AM transmitter produces 10 kW. How much of this is carrier power? Show Answer

Q250) To cover a population of 20 lakh, a transmission tower should have a height … (Radius of earth = 6400 km, population per square km =1000) Show Answer

Q251) A sky wave with a frequency 55 MHz is incident on the D-region of earth's atmosphere at30°. The angle of refraction is (electron density for D-region is 400 electron/cc) Show Answer

Q252) The fundamental radio antenna is a metal rod which has a length equal to Show Answer

Q253) Let A = light obtained by stimulated emission and B = light obtained by spontaneous, then Show Answer

Q254) The antenna current of an AM transmitter is 8 A when only carrier is sent but increases to 8.96 A when the carrier is sinusoidally modulated. The percentage modulation is Show Answer

Q255) In earth's atmosphere, for F1-layer; the virtual height and critical frequency are Show Answer

Q256) A signal wave of frequency 12 kHz is modulated with a carrier wave of frequency 2.51 MHz. The upper and lower side band frequencies are respectively Show Answer

Q257) The K line of singly ionized calcium has a wavelength of 393.3 nm as measured on earth. In the spectrum of one of the observed galaxies, this spectral line is located at 401.8 nm. The speed with which the galaxy is moving away from us, will be Show Answer

Q258) An oscillator is producing FM waves of frequency 2 kHz with a variation of 10 kHz. What is the modulating index? Show Answer

Q259) A transmitter supplies 9 kW to the aerial when unmodulated. The power radiated when modulated to 40% is Show Answer

Q260) Sinusoidal carrier voltage of frequency 1.5 MHz and amplitude 50 V is amplitude modulated by sinusoidal voltage of frequency 10 kHz producing 50% modulation. The lower and upper side-band frequencies in kHz are Show Answer

Q261) The velocity factor of a transmission line is x. If dielectric constant of the medium is 2.6, the value of x is Show Answer

Q262) An amplitude modulated wave is modulated to 50%. What is the saving in power if carrier as well as one of the side bands are suppressed Show Answer

Q263) The distance of coverage of a transmitting antenna is 12.8 km. Then, the height of the antenna is (Given that radius of earth = 6400 km) Show Answer

Q264) A telephone link operating at a central frequency of 10 GHz is established. If 1% of this available then how many telephone channels can be simultaneously given when each telephone covering a band width of 5 kHz Show Answer

Q265) Arrange the following communication frequency bands in the increasing order of frequencies 1. AM broadcast
2. Cellular mobile radio
3. F.M. broadcast
4. Television UHF
5. Satellite communication Show Answer

Q266) Electromagnetic waves with frequencies greater than the critical frequency of ionosphere cannot be used for communication using sky wave propagation, because Show Answer

Q267) For good demodulation of AM signal of carrier frequency f, the value of RC should be Show Answer

Q268) The wavelength of red light from He-Ne laser is 633 nm in air but 474 nm in the aqueous humor inside the eye ball. Then the speed of red light through the aqueous humor is Show Answer

Q269) The sky wave propagation is suitable for radio-waves of frequency Show Answer

Q270) For sky wave propagation of 10 MHz signal, what should be the minimum electron density in ionosphere? Show Answer

Q271) The antenna current of an AM transmitter is 8 A when only the carrier is sent, but it increases to 8.93 A when the carrier is sinusoidal modulated. The percentage modulation is nearly Show Answer

Q272) What is the value of frequency at which electromagnetic wave must be propagated for the D-region of atmosphere to have a refractive index of 0.5. Electron density for D-region is 400 electrons/cc Show Answer

Q273) Which frequency range is used for optical communication? Show Answer

Q274) A TV tower has a height of 75 m. What is the maximum area upto which this TV communication can be possible? Show Answer

Q275) If both the length of an antenna and the wavelength of the signal to be transmitted are doubled, the power radiated by the antenna Show Answer

Q276) An AM wave has 1800 watt of total power content. For 100% modulation the carrier should have power content equal to Show Answer

Q277) What is the modulation index of an over modulated wave Show Answer

Q278) In AM, the centpercent modulation is achieved when Show Answer

Q279) What should be the velocity of an object so that it’s mass becomes twice of its rest mass? Show Answer

Q280) An antenna behaves as resonant circuit only when its length is Show Answer

Q281) 1000 kHz carrier wave is amplitude modulated by the signal frequency 200-4000 Hz. The channel width of this case is Show Answer

Q282) The range of characteristics impedance for co-axial wire lines is Show Answer

Q283) If the maximum amplitude of an amplitude modulated wave is 25 V and the minimum amplitude is 5 V, the modulation index is Show Answer

Q284) What happens inside optical fibre? Show Answer

Q285) With reference to ionospheric propogation, an electromagnetic wave with a critical frequency of 15 MHz and incident at an angle of 45° will have MUF of Show Answer

Q286) The velocity factor of a transmission line is related to dielectric constant K of the medium is Show Answer

Q287) Day time ionosphere comprises of Show Answer

Q288) The transmission of high frequencies in a coaxial cable is determined by Show Answer

Q289) The maximum distance upto which TV transmission from a TV tower of height h can be received is proportional to Show Answer

Q290) The energy of an electromagnetic wave contained in a small volume oscillates with Show Answer

Q291) Which of the following Maxwell's equation is valid for time varying conditions but not valid for static conditions Show Answer

Q292) In an electromagnetic wave, at an instant and at a particular position, the electric field is along the negative Z-axis and magnetic field is along the positive X-axis. Then, the direction of propagation of electromagnetic wave is Show Answer

Q293) The ratio of average electric energy density and total average energy density of electromagnetic wave is Show Answer

Q294) A point source of 100 W emits light with 5% efficiency. At a distance of 5 m from the source, the intensity produced by the electric field component is Show Answer

Q295) An electromagnetic wave is transporting energy in the negative z-direction. At a certain point and certain time, the direction of electric field of the wave is along positive y-direction. What will be the direction of the magnetic field of the wave at that point and instant? Show Answer

Q296) Which of the following are true?
A. Speed of light in vacuum is dependent on the direction of propagation.
B. Speed of light in a medium is independent of the wavelength of light.
C. The speed of light is independent of the motion of the source.
D. The speed of light in a medium is independent of intensity.
Choose the correct answer from the options given below

Show Answer

Q297) Identify the correct statements from the following descriptions of various properties of electromagnetic waves:
(A) In a plane electromagnetic wave, electric field and magnetic field must be perpendicular to each other and direction of propagation of wave should be along electric field or magnetic field. (B) The energy in electromagnetic wave is divided equally between electric and magnetic fields.
(C) Both electric field and magnetic field are parallel to each other and perpendicular to the direction of propagation of wave.
(D) The electric field, magnetic field and direction of propagation of wave must be perpendicular to each other.
(E) The ratio of amplitude of magnetic field to the amplitude of electric field is equal to speed of light. Choose the most appropriate answer from the options given below.
Show Answer

Q298) The rms value of conduction current in a parallel plate capacitor is 6.9 μA. The capacity of this capacitor, if it is connected to 230 V AC supply with an angular frequency of 600 rad/s, will be Show Answer

Q299) A plane electromagnetic wave propagating along y-direction can have the following pair of electric field (E) and magnetic field (B) components. Show Answer

Q300) A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the light at a distance of 1 m from the diode is Show Answer

Q301) For plane electromagnetic waves propagating in the z-direction, which one of the following combination the correct possible direction for field, respectively? Show Answer

Q302) The magnetic field in a travelling electromagnetic wave has a peak value of 20 nT. The peak value of electric field strength is
Show Answer

Q303) An electromagnetic wave in vacuum has the electric is and magnetic fields E and B, which are always perpendicular to each other. The direction of polarisation is given by X and that of wave propagation by k. Then, Show Answer

Q304) A radiation of energy E falls normally on a perfectly reflecting surface. The momentum transferred to the surface is Show Answer

Q305) Electromagnetic waves are transverse in nature is
evident by
Show Answer

Q306) In a medium, the speed of light wave decreases to 0.2 times to its speed in free space. The ratio of relative permittivity to the refractive index of the medium is .... Show Answer

Q307) An electromagnetic wave of frequency
v=3.0 MHz passes from vacuum into a dielectric medium with permittivity & = 4.0. Then, Show Answer

Q308) Given below are two statements, one is labelled as :
Assertion (A) and the other is labelled as Reason (R). Assertion (A) EM waves used for optical communication have longer wavelengths than that of microwave, employed in Radar technology. Reason (R) Infrared EM waves are more energetic than microwaves, (used in Radar)
In the light of the above statements, choose the most appropriate answer from the options given below.
Show Answer

Q309) Which is the correct ascending order of wavelength? Show Answer

Q310) Arrange the following electromagnetic radiations quantum in the order of increasing energy.
A.Blue light
B. Yellow light
C. X-ray
D. Radio wave Show Answer

Q311) Which of the following are not electromagnetic Suley waves? Show Answer

Q312) By what percentage will the transmission range of a TV tower be affected when the height of the tower is increased by 21% ? Show Answer

Q313) In satellite communication, the uplink frequency band used is Show Answer

Q314) The power radiated from a linear antenna of length l is proportional to
(Given, Lambda =Wavelength of wave): Show Answer

Q315) A TV transmitting antenna is at the ground level. If the radius of the earth is 6400 km, the surface area covered by the transmitting is approximately Show Answer

Q316) To radiate EM signal of wavelength lambda with high efficiency, the antennas should have a minimum size equal to Show Answer

Q317) The height of transmitting antenna is 180 m and the height of the receiving antenna is 245m. The maximum distance between them for satisfactory communication in line of sight will be (given, R=6400 km) Show Answer

Q318) If the height of transmitting and receiving antennas are 80m each, the maximum line of sight distance will be Show Answer

Q319) Which of the following frequencies does not belong to FM broadcast? Show Answer

Q320) At a particular station, the TV transmission tower has a height of 100. To triple its coverage range, height of the tower should be increased to Show Answer

Q321) The TV transmission tower at a particular station has a height of 125m. For doubling the coverage of its range, the height of the tower should be increased by Show Answer

Q322) We do not transmit low frequency signal to long distances because
(A)The size of the antenna should be comparable to signal wavelength which is unreal solution for a signal of longer wavelength.
(B)Effective power radiation by a long wavelength baseband signal would be high.
(C)We want to avoid mixing up signals transmitted by different transmitter simultaneously.
(D)Low frequency signal can be sent to long distances by superimposing with a high frequency wave as well
Therefore the most suitable option will be Show Answer

Q323) The signal of 100 THz frequency can be transmitted with maximum efficiency by Show Answer

Q324) An antenna is mounted on a 400m tall building. What will be the wavelength of signal that can be radiated effectively by the transmission tower upto a range of 44 km? Show Answer

Q325) A transmitting antenna at top of a tower has a height of 50m and the height of receiving antenna is 80m. What is range of communication for line of sight (LOS) mode?[ Use radius of Earth= 6400 km] Show Answer

Q326) Two identical antennas mounted on identical towers are separated from each other by a distance of 45 km. What should nearly be the minimum height of receiving antenna to receive the signals in line of sight ? [Assume, radius of earth is 6400 km] Show Answer

Q327) A 25m long antenna is mounted on an antenna tower. The height of the antenna tower is 75m. The wavelength (in m) of the signal transmitted by this antenna would be Show Answer

Q328) In a line of sight radio communication, a distance of about 50 km is kept between the transmitting and receiving antennas. If the height of the receiving antenna is 70m, then the minimum height of the transmitting antenna should be Show Answer

Q329) A telephonic communication service is working at carrier frequency of 10 GHz. Only 10% of it is utilised for transmission. How many telephonic channels can be transmitted simultaneously, if each channel requires a bandwidth of 5 kHz ? Show Answer

Q330) Long range radio transmission is possible when the radio waves are reflected from the ionosphere. For this ti happen, the frequency of the radio waves must be in the range: Show Answer

Q331) A radar has a power of 1 kW and is operating at a frequency of 10 GHz. The maximum distance upto which it can detect the object located on the surface of the earth is: Show Answer

Q332) This question has Statement I and Statement II. Of the four choices given after the statements, choose the one that best describes the two statements.
Statement I Sky wave signal are used for long distance radio communication. These signals are in general, less stable than ground wave signals.
Statements II The state of ionosphere varies from hour to hour, day to day and season to season. Show Answer

Q333) Consider telecommunication through optical fibres. Which of the following statements is not true? Show Answer

Q334) A message signal of frequency 3kHz is used to modulate a carrier signal of frequency 1.5 MHz. The bandwidth of the amplitude modulated wave is Show Answer

Q335) A carrier wave of amplitude 15 V is modulated by a sinusoidal base band signal of amplitude 3 V. The ratio of maximum amplitude to minimum amplitude in an amplitude modulated wave is: Show Answer

Q336) For a amplitude modulated wave the minimum amplitude is 3V, while the modulation index is 60%. The maximum amplitude of the modulated wave is Show Answer

Q337) Given below are two statements
Statement I For transmitting a signal, size of antenna (l) should be comparable to wavelength of signal (at least l=lambda/4 in dimension)
Statement II In amplitude modulation, amplitude of carrier wave remains constant (unchanged).
In the light of the above statements, choose the most appropriate answer from the options given below. Show Answer

Q338) In an amplitude modulation, a modulating signal having amplitude of X volt is superimposed with a carrier signal of amplitude Y volt in first case. Then, in second case, the same modulating signal is superimposed with different carrier signal is superimposed with different carrier signal of amplitude 2Y volt. The ratio of modulation index in the two cases respectively will be Show Answer

Q339) The modulation index for an AM wave having maximum and minimum peak to peak voltages of 14 mV and 6 mV respectively is Show Answer

Q340) A message signal of frequency 5 kHz is used to modulate a carrier signal of frequency 2 MHz. The bandwidth for amplitude modulation is Show Answer

Q341) Find the modulation index of an AM wave having 8V variation where maximum amplitude of the AM wave is 9V. Show Answer

Q342) A FM broadcast transmitter , using modulating signal of frequency 20 kHz has a deviation ratio of 10. The bandwidth required for transmission is Show Answer

Q343) In the case of amplitude modulation to avoid distortion the modulation index should be Show Answer

Q344) The maximum and minimum voltage of an amplitude modulated signal are 60 V and 20 V respectively. The percentage of modulation index will be Show Answer

Q345) A radio tune to any station in 6 MHz to 10 MHz band. The value of corresponding wavelength bandwidth will be Show Answer

Q346) In AM modulation, a signal is modulated on a carrier wave such that maximum and minimum amplitudes are found to be 6V and 2V, respectively. The modulation index is Show Answer

Q347) Only 2% of the optical source frequency is the available channel bandwidth for an optical communicating system operating at 1000 nm. If an audio signal requires a bandwidth of 8 kHz, how many channels can be accommodated for transmission? Show Answer

Q348) Choose the correct statements for amplitude modulation. Show Answer

Q349) A baseband signal of 3.5 MHz frequency is modulated with a carrier signal of 3.5 GHz frequency using amplitude modulation method. What should be the minimum size of antenna required to transmit the modulated signal? Show Answer

Q350) Given below are two statements
Statement I A speech signal of 2 kHz is used to modulate a carrier signal of 1 MHz. The bandwidth requirement for the signal is 4 kHz.
Statement II The side band frequencies are 1002 kHz and 998 kHz. In the light of the above statements, choose the correct answer from the options given below. Show Answer

Q351) A message of frequency 100 MHz and peak voltage 100 V is used to execute amplitude modulation on a carrier wave of frequency 300 GHz and peak voltage 400 V. The modulation index and difference between the two side bands frequencies are Show Answer

Q352) Choose the correct statement Show Answer