Question

A point source of light is used in an experiment on photoelectric effect. Which of the following curves best represents the variation of photocurrent 'I' with distance 'd' of the source from the emitter:

• A. A
• B. B
• C. C
• D. D

Answer 1

Answer: (A)

A

We know that with an increase in distance of the source from emitter the intensity of radiation is gradually decreased. Hence the photocurrent also decreases.

Intensity on photons on emitter varies as:

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

The photoelectric current is directly proportional to the intensity of photons.

$i\propto I$

So, $i\propto \frac{1}{d^2}$

therefore the graph that is correct is (A).