Question

In a $p-n$ junction photo cell, the value of the photo electromotive force produced by monochromatic light is proportional to

• A. the barrier voltage at the $p-n$ junction.
• B. the intensity of the light falling on the cell.
• C. the frequency of the light falling on the cell.
• D. the voltage applied at the $p-n$ junction.

Answer 1

The correct option is B the intensity of the light falling on the cell.

The electromotive force is similar to the potential difference. According to Ohm’s law, a potential difference is directly proportional to the current and resistance. Hence, the electromotive force is also proportional to the current.

As we know that,

$\text{Intensity of the light}=\frac{\text{power of the light}}{\text{area}}$.

And,

$\text{Power}\propto \text{current}\propto \text{electromotive force}$

$\therefore \text{Electromotive force}\propto \text{Intensity of the light}$

Hence, $\left(B\right)$ is the correct answer.