Question

The anode voltage of a photocell is kept fixed. The wavelength $\lambda$ of the light falling on the cathode is gradually changed. The plate current $I$ of the photocell varies with $\lambda$ as follows :

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

Let $I$ be the current and $I_{int}$ be the intensity.

Each photon gives rise to one photoelectron. Also, intensity is proportional to incident photons and energy of each photon.

Hence, $I\propto I_{int}\propto E$

Energy of a photon, $E=hc/\lambda$

$\therefore I\propto \frac{1}{\lambda }$

Hence, option $\left(\text{C}\right)$ is the correct answer of the given equation.