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 as follows

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

Let Current be $I$ and intensity be $I_{int}$
Each photon gives rise to one photoelectron. Also, intensity is proportional to incident photons and energy of each photon.

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

Energy of a photon, $E=\frac{hc}{\lambda }I\propto \frac{1}{\lambda }$
Hence, option $D$ is correct.