A photocell with a constant potential difference of V volt across it is illuminated by a point source from a distance of 25 cm. When the source is moved to a distance of 1m. The electrons are emitted by the photocell:
Correct answer: B. Are 1/16th as numerous as before
- A. Carry 1⁄4th of their previous energy
- B. Are 1/16th as numerous as before
- C. Carry 1⁄4th as their previous energy
- D. Carry 1/4th as their previous momentum
Explanation
I2/I1= (r1/r2)2As r1= 0.25mAnd r2= 1m we have I2/I1=1/16This is correct based on the change in intensity. If the intensity decreases by a factor of 1/16, the number of electrons emitted will decrease by the same factor.
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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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