For a given photosensitive material, the stopping potential Vo varies with the frequency of incident radiation as

linearly with frequency

The correct answer is Option (2) → linearly with frequency

According to the photoelectric effect, the maximum kinetic energy of emitted electrons is:

$K_{\text{max}} = h f - \phi$

Stopping potential $V_0$ is related by $e V_0 = K_{\text{max}}$

So, $V_0 = \frac{h}{e} f - \frac{\phi}{e}$

This shows $V_0$ varies linearly with the frequency f.