A photocell with a constant potential difference of V volts across it illuminated by a point source from a distance of 25 cm. When the source is moved to a distance of 1m, the electrons emitted by the photocell
Correct answer: D. Carry 1/4th their previous momentum
- A. Carry ¼th their previous energy
- B. Are 1/16th as numerous as before
- C. Are 1/4th as numerous as before
- D. Carry 1/4th their previous momentum
Explanation
Correct. The kinetic energy (and therefore momentum) of photoelectrons is determined by the potential difference and is independent of the distance to the source.In summary, the correct option is **d. Carry 1/4th their previous momentum** based on the nature of photoelectric emission
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Classical physics cannot explain blackbody radiation and related observations, leading to Planck’s quantum theory, in which energy is emitted or absorbed in discrete packets. Photons provide the particle model of light, with energy and momentum linked to frequency and wavelength, including the photoelectric effect and its threshold frequency.
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