Question

A point source causes photoelectric effect from a small metal plate. Which of the following curves , may well represent the saturation photo current as a function of the distance between the source and the metal?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

We know that photo current directly proportional to intensity of the incident light. But intensity is inversely proportional to the square of the distance.

$\Rightarrow i\propto I\propto \frac{1}{d^2}$

$[\because I=\frac{P}{4\pi d^2}]$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(D\right)$ is the correct answer.