From the figure describing photoelectric effect we may infer corr

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 Multiple Choice QuestionsMultiple Choice Questions

41.

Threshold wavelength for photoelectric emission from a metal surface is 5200 A. Photoelectrons will be emitted when this surface is illuminated with monochromatic radiation from

  • 1 W IR lamp

  • 50 W UV lamp

  • 50 W IR lamp

  • 10 W IR lamp


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42.

From the figure describing photoelectric effect we may infer correctly that

            

  • Na and Al both have the same threshold frequency

  • maximum kinetic energy for both the metals depend linearly on the frequency

  • the stopping potentials are different for Na and Al for the same change in frequency

  • Al is a better photo sensitive material than Na


B.

maximum kinetic energy for both the metals depend linearly on the frequency

The graph between stopping potential and frequency is a straight line, so stopping potential and hence, maximum kinetic energy of photoelectrons depends linearly on the frequency.


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43.

When light of wavelength 300 nm falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, light of wavelength 600 nm is suffcient for liberating photoelectrons. The ratio of the work function of the two emitters is

  • 1 : 2

  • 2 : 1

  • 4 : 1

  • 1 : 4


44.

Maxium velocity of the photoelectrons emitted by a metal surface is 1.2 x 106 ms-1. Assuming the specific charge of the electron to be 1.8 x 1011 C kg-1, the value of the stopping potential in volt will be

  • 2

  • 3

  • 4

  • 6


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45.

Which one of the following graph represents the variation of maximum kinetic energy (Ek) of the emitted electrons with frequency v in photoelectric effect correctly ?


46.

A and B are two metals with threshold frequencies 18 x 1014 Hz and 2.2 x 1014 Hz. Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted by (Take h = 6.6 x 10-34 J-s)

  • B alone

  • A alone

  • neither A nor B

  • both A and B


47.

The electromagnetic theory of light failed to explain

  • photoelectric effect

  • polarisation

  • diffraction

  • interference


48.

When a piece of metal is illuminated by a monochromatic light of wavelength λ, then stopping potential is 3Vs. When same surface is illuminated by light of wavelength 2λ, then stopping potential becomes Vs. The value of threshold wavelength for photoelectric emission will be

  • 43λ


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49.

The maximum kinetic energy of emitted electrons in a photoelectric effect does not depend upon

  • wavelength

  • frequency

  • intensity

  • work function


50.

The amount of energy released when one microgram of matter is annihilated is

  • 25 kWh

  • 9 × 1010 kWh

  • 3 × 1010 kWh

  • 0.5 × 105 kWh


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