The maximum kinetic energy of photoelectrons from Physics Dual N

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 Multiple Choice QuestionsMultiple Choice Questions

21.

The maximum velocities of the photoelectrons ejected are v and 2v for the incident light of wavelength 400 nm and 250 nm on a metal surface respectively. The work function of the metal in terms of Planck's constant h and velocity of light c is

  • hc × 106 J

  • 2 hc × 106 J

  • 1.5 hc × 106 J

  • 2.5 hc × 106 J


22.

If the frequency of incident light falling on a photosensitive metal is doubled, the kinetic energy of the emitted photoelectron is

  • unchanged

  • halved

  • doubled

  • more than twice its initial value


23.

The work functions of two metals are 2.75 eV respectively. If these are irradiated by photons of energy 3 eV, the ratio of maximum momenta of the photoelectrons emitted respectively by them is

  • 1 : 2

  • 1 : 3

  • 1 : 4

  • 2 : 1


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24.

The maximum kinetic energy of photoelectrons

  • depends on collector plate

  • is independent of emitter plate material

  • is independent of frequency of incident radiation

  • depends on the frequency of light source and the nature of emitter plate material


D.

depends on the frequency of light source and the nature of emitter plate material

We have,

 hv = hv0 + KEmax

Here, KEmax depends on v and hv0.

Hence, we can say that the maximum KE of photoelectrons depends on the frequency of light source and the nature of emitter plate materials.


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25.

If e/m of electron is 1.76 x 1011 C kg-1 and the stopping potential is 0.71 V, then the maximum velocity of the photo-electron is

  • 150 kms-1

  • 200 kms-1

  • 500 kms-1

  • 250 kms-1


26.

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

  • c2mE

  • 2mE

  • 2mcE

  • mE


27.

When a metallic surface is illuminated by a light of wavelength λ, the stopping potential for the photoelectric current is 3 V. When the same surface is illuminated by light of wavelength 2λ, the stopping potential is 1 V, the threshold wavelength for this surface is

  • 4 λ

  • 3.5 λ

  • 3 λ

  • 2.75 λ


28.

The threshold wavelength for photoelectric emission from a material is 4800 A. Photoelectrons will be emitted from the material, when it is illuminated with light from a

  • 40 W blue lamp

  • 40 W green lamp

  • 100 W red lamp

  • 100 W yellow lamp


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29.

When a monochromatic point source of light is at a distance 0.2 m from a photoelectric cell, the saturation current and cut-off voltage are 12.0 mA and 0.5 V. If the same source is placed 0.4 m away from the photoelectric cell, then the saturation current and the stopping potential respectively are

  • 4 mA and 1 V

  • 12 mA and 1 V

  • 3 mA and 0.5 V

  • 12 mA and 0.5 V


30.

A photodetector used to detect the wavelength of 1700 nm, has energy gap of about

  • 0.073 eV

  • 1.2 eV

  • 0.73 eV

  • 1.16 eV


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