Question

A photoelectric cell is lightened by a light source, situated at a distance d from the cell. If distance becomes $d/2$ then number of electrons emitted per sec will be:-

• A. Remains same
• B. Four times
• C. Two times
• D. One fourth

Answer 1

The correct option is B Four times

Intensity is directly proportional to number of photons $incident$ on the surface.

$Intensity\propto \frac{1}{distanc{e}^2}$

so on making distance $1/2$ we will get intensity $(\frac{1}{1/2}{)}^2=4$ $times$

One photon contribute in one electrons so the number of electrons will also become $4$ times.