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प्रश्न
Light of wavelength 488 nm is produced by an argon laser which is used in the photoelectric effect. When light from this spectral line is incident on the emitter, the stopping (cut-off) potential of photoelectrons is 0.38 V. Find the work function of the material from which the emitter is made.
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उत्तर
Wavelength of light produced by the argon laser, λ = 488 nm = 488 × 10−9 m
Stopping potential of the photoelectrons, V0 = 0.38 V
Planck’s constant, h = 6.6 × 10−34 Js
Charge on an electron, e = 1.6 × 10−19 C
Speed of light, c = 3 × 108 m/s
From Einstein’s photoelectric effect, we have the relation involving the work function `phi_0` of the material of the emitter as:
`eV_0 = (hc)/lambda - phi_0`
`phi_0 = (hc)/lambda - eV_0`
= `(6.6 xx 10^(-34 ) xx 3 xx 10^8)/(488 xx 10^(-9)) - 1.6 xx 10^(-19) xx 0.38`
= 2.54 − 0.38
= 2.16 eV
Therefore, the material with which the emitter is made has the work function of 2.16 eV.
संबंधित प्रश्न
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Write Einstein’s photoelectric equation?
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Using Einstein’s photoelectric equation shows how the cut-off voltage and threshold frequency for a given photosensitive material can be determined with the help of a suitable plot/graph.
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(B) The maximum kinetic energy of the photoelectrons is doubled.
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- Why is this fact (two photon absorption) not taken into consideration in our discussion of the stopping potential?
There are materials which absorb photons of shorter wavelength and emit photons of longer wavelength. Can there be stable substances which absorb photons of larger wavelength and emit light of shorter wavelength.
Radiation of frequency 1015 Hz is incident on three photosensitive surfaces A, B and C. Following observations are recorded:
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Surface B: photoemission occurs but the photoelectrons have zero kinetic energy.
Surface C: photo emission occurs and photoelectrons have some kinetic energy.
Using Einstein’s photo-electric equation, explain the three observations.
