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in Physics by (44.7k points)

Photocell cell is enlightended by small bright source 1 m away. If the same light source is placed (1/2) m away, number of electrons emitted by cathode will be…….. 

(A) increases twice 

(B) decreases twice 

(C) increases 4 times 

(D) decreases 4 times

1 Answer

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Best answer

The correct option is (C) increases 4 times.

Explanation:

Intensity of light radiation = I ∝ (1 / r2)

Distance r is changed by (1/2) hence intensity will increase by factor of (2)2

i.e. 4.

Hence rate of photoelectron emission from photo cathode also increases by q factor of 4.

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