Question

A point source causing photoelectric emission from a metallic plate is moved away from the plate. The variation of photoelectric current with distance from the source is correctly represented by the graph ______.
Fill in the blank with the correct answer from the options given below

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is B

The photoelectric effect occurs when light incident on a metal surface causes the emission of electrons. The photoelectric current (the rate of electron flow) depends on the intensity of the incident light, which decreases with distance from the light source according to the inverse square law. As the distance from the point source increases, the intensity of the light, and consequently the photoelectric current, decreases proportionally to the square of the distance. 

Mathematically, this relationship can be expressed as:

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

where $I$ is the intensity of light, and $d$ is the distance from the light source. Therefore, the photoelectric current is also proportional to the reciprocal of the square of the distance.

The correct graph representing this relationship is a curve that shows the photoelectric current decreasing with increasing distance, consistent with the graph labeled as "Graph (II)".