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कर्नाटक बोर्ड पी.यू.सी.पीयूसी विज्ञान इयत्ता ११

A Photon of Energy Hv is Absorbed by a Free Electron of a Metal with Work-function Hv − φ.

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प्रश्न

A photon of energy hv is absorbed by a free electron of a metal with work-function hv − φ.

पर्याय

  • The electron is sure to come out.

  • The electron is sure to come out with kinetic energy hv − φ.

  • Either the electron does not come out or it comes our with kinetic energy hv − φ.

  • It may come out with kinetic energy less than hv − φ.

MCQ
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उत्तर

It may come out with kinetic energy less than hv − φ.

When light is incident on the metal surface, the photons of light collide with the free electrons. In some cases, a photon can give all the energy to the free electron. If this energy is more then the work-function of the metal,then there are two possibilities. The electron can come out of the metal with kinetic energy hv − φ or it may lose energy on collision with the atoms of the metal and come out with kinetic energy less than hv − φ. Thus, it may come out with kinetic energy less than hv − φ.

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  या प्रश्नात किंवा उत्तरात काही त्रुटी आहे का?
पाठ 42: Photoelectric Effect and Wave-Particle Duality - MCQ [पृष्ठ ३६४]

APPEARS IN

एचसी वर्मा Concepts of Physics Volume 1 and 2 [English]
पाठ 42 Photoelectric Effect and Wave-Particle Duality
MCQ | Q 3 | पृष्ठ ३६४

संबंधित प्रश्‍न

(a) Estimate the speed with which electrons emitted from a heated emitter of an evacuated tube impinge on the collector maintained at a potential difference of 500 V with respect to the emitter. Ignore the small initial speeds of the electrons. The specific charge of the electron, i.e., its e/m is given to be 1.76 × 1011 C kg−1.

(b) Use the same formula you employ in (a) to obtain electron speed for an collector potential of 10 MV. Do you see what is wrong? In what way is the formula to be modified?


The work function for the following metals is given: 

Na: 2.75 eV; K: 2.30 eV; Mo: 4.17 eV; Ni: 5.15 eV

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Draw graphs showing variation of photoelectric current with applied voltage for two incident radiations of equal frequency and different intensities. Mark the graph for the radiation of higher intensity.


Let nr and nb be the number of photons emitted by a red bulb and a blue bulb, respectively, of equal power in a given time.


The equation E = pc is valid


Light of wavelength λ falls on a metal with work-function hc/λ0. Photoelectric effect will take place only if


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(b) the maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity
(c) even when the metal surface is faintly illuminated the photoelectrons leave the surface immediately
(d) electric charge of the photoelectrons is quantised


The collector plate in an experiment on photoelectric effect is kept vertically above the emitter plate. A light source is put on and a saturation photocurrent is recorded. An electric field is switched on that has a vertically downward direction.


The work function of a photoelectric material is 4.0 eV. (a) What is the threshold wavelength? (b) Find the wavelength of light for which the stopping potential is 2.5 V.

(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)


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Wavelength (nm):         350   400   450   500   550
Stopping potential (V): 1.45  1.00  0.66  0.38  0.16

Plot the stopping potential against inverse of wavelength (1/λ) on a graph paper and find (a) Planck's constant (b) the work function of the emitter and (c) the threshold wavelength.

(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)


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The work function for a metal surface is 4.14 eV. The threshold wavelength for this metal surface is ______.


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  1. What does X and A on the horizontal axis represent?
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  3. Draw this graph for three different values of intensities of incident radiation I1, I2 and I3 (I3 > I2 > I1) having the same frequency.

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What is the effect of threshold frequency and stopping potential on increasing the frequency of the incident beam of light? Justify your answer.


Which of the following options represents the variation of photoelectric current with property of light shown on the x-axis?






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