In photoelectric effect, the electrons are ejected from meta

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 Multiple Choice QuestionsMultiple Choice Questions

111.

The work function of sodium is 2.3 eV. The threshold wavelength of sodium will be

  • 2900 Ao

  • 2500 Ao

  • 5380 Ao

  • 1200 Ao


112.

The minimum wavelength of X-ray emitted by X-ray tube is 0.4125 Ao. The accelerating voltage is

  • 30 kV

  • 50 kV

  • 80 kV

  • 60 kV


113.

The light rays having photons of energy 1.8 eV are falling on a metal surface having a work function 1.2 eV. What is the stopping potential to be applied to stop the emitting electrons?

  • 3 eV

  • 1.2 eV

  • 0.6 eV

  • 1.4 eV


114.

A light passing through air has wavelength 6000 Ao. The wavelength when same ray passes through a glass slab of refractive index 1.5 will be:

  • 2000 Ao

  • 4000 Ao

  • 8000 Ao

  • 1200 Ao


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115.

The work functions for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV. According to Einstein's equation, the metals which will emit photoelectrons for a radiation length 4100 Ao is /are 

  • none

  • A only

  • A and B only

  • all the three metals


116.

 The nuclei of which one of the following pairs
of nuclei are isotones ?

  • Se 7434,  Ga 7131

  • Mo 9242,  Zr 9240

  • Sr 8438,  Sr 8638

  • Ca4020,  S 3216


117.

The ratio of the dimensions of Planck's constant and that of the moment of inertia is the dimension of

  • frequency

  • velocity

  • angular momentum

  • time


118.

A photosensitive metallic surface has work function, h vo, If photons of energy 2hvo, fall on this surface, the electrons come out with a maximum velocity of 4 x 106 m/s. When the photon energy is increased to 5 hv,, then maximum velocity of photoelectrons will be

  • 2 × 106 m/s

  • 2 × 107 m/s

  • 8 × 105 m/s

  • 8 × 106 m/s


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119.

Hard X-rays for the study of fractures in bones should have a minimum wavelength of 10' m. The accelerating voltage for electrons in X-ray machine should be

  • < 124 kV

  • > 124 kV

  • between 60 kV and 70 kV

  • = 100 kV


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120.

In photoelectric effect, the electrons are ejected from metals if the incident light has a certain minimum

  • wavelength

  • frequency

  • amplitude

  • angle of incidence


B.

frequency

In photoelectric effect for a given photosensitive material, there exists a certain minimum cut-off frequency, called the threshold frequency, below which no emission of photoelectrons takes place no matter how intense the light is.


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