Question

A photoelectric cell is illuminated by a point source of light $1m$ away. When the source is shifted to $2m$ then :

• A. each emitted electron carries half the initial emergy
• B. number of electrons emitted is a quarter of the initial number
• C. each emitted electron caries one quarter of the initial energy
• D. number of electrons emitted is half the initial number

Answer 1

The correct option is B number of electrons emitted is a quarter of the initial number

Number of photoelectrons emitted per second is directly proportional to intensity of light
Intensity of light source is
$I\propto \frac{1}{d^2}$
When distance is doubled, intensity becomes one-fourth
As number of photoelectrons $\propto$ intensity, so number of photoelectrons is quarter of the initial number.