Threshold wavelength for photoelectric emission from a metal surf

Previous Year Papers

Download Solved Question Papers Free for Offline Practice and view Solutions Online.

Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.
Advertisement

 Multiple Choice QuestionsMultiple Choice Questions

Advertisement

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


B.

50 W UV lamp

For photoelectric emission to take place the wavelength of incident light must be less than the threshold value which is given as 5200 A.

The wavelength of infra-red light = 7800 A

The wavelength of ultra-violet light = 4000 A

Thus, it is obvious the wavelength of UV radiation is less than the threshold value. Hence, it can emit photoelectrons from the surface of metal.


Advertisement
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


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


Advertisement
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


Advertisement
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


Advertisement