In photoelectric effect, the number of electrons ejected per seco

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 Multiple Choice QuestionsMultiple Choice Questions

31.

In a photoelectric effect measurement, the stopping potential for a given metal is found to be V volt when radiation ofwavelength λ0 is used. If radiation of wavelength 2λ0 is used with the same metal then the stopping potential (in volt) will be

  • V02

  • 2V0

  • V0 + hc2 0

  • V0 - hc2 0


32.

The wavelength of a 1 keV photon is 1.24 nm. The frequency of 1 MeV photon is

  • 1.24 × 1015 Hz

  • 2.4 × 1020 Hz

  • 1.24 × 1018 Hz

  • 2.4 × 1024 Hz


33.

A photon of energy 8 eV is incident on metal surface of threshold frequency 1.6 x 1015 Hz. The kinetic energy of the photoelectrons emitted (in eV) : (Take h = 6 x 10-34 J-s)

  • 1.6

  • 6

  • 2

  • 1.2


34.

The rest mass of photon is

  • hvc

  • hvc2

  • hcλ

  • zero


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35.

If the wavelength of incident light changes from 400 nm to 300 nm, the stopping potential for photoelectrons emitted from a surface becomes approximately

  • 1.0 V greater

  • 1.0 V smaller

  • 0.5 V greater

  • 0.5 V smaller


36.

A radio transmitter radiates 1 kW power at a wavelength 198.6 m. How many photons does it emit per second ?

  • 1010

  • 1020

  • 1030

  • 1040


37.

If the speed of light were 2/3 of its present value, the energy released in a given atomic explosion would

  • decrease by a factor 2/3

  • decrease by a factor 4/9

  • decrease by a factor 5/9

  • decrease by a factor 59


38.

The rate of emission of a black body at 0°C is R, its rate of emission at 273°C is

  • 4 R

  • 8 R

  • 16 R

  • 32 R


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39.

There are n1 photons of frequency v1 in a beam oflight. In an equally energetic beam there are n2 photons of frequency v2. Then the correct relation

  • n1n2 = v1v2

  • n1n2 = 1

  • n1n2 = v2v1

  • n1n2 = v22v12


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40.

In photoelectric effect, the number of electrons ejected per second is

  • proportional to the wavelength of light

  • proportional to the intensity of light

  • proportional to the work function of the metal

  • proportional to the frequency of light


B.

proportional to the intensity of light

The number of electron ejected per second is directly proportional to the intensity of light.


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