(a) Variation of photocurrent with intensity of radiation (b) Stopping potential versus frequency for different materials (c) Independence of maximum kinetic energy of the emitted photoelectrons (a) The collision of a photon can cause emission of a photoelectron (above the threshold frequency). As intensity increases, number of photons increases. Hence the current increases. (b) We have, $e V_s = h (v - v_0)$ $\therefore V_s = \frac{h}{e}(v) + \left( -\frac{h v_0}{e} \right)$ ∴ Graph of $V_s$ with $v$ is a straight line and slope $\left(= \frac{h}{e}\right)$ is a constant. (c) Maximum for different surfaces $KE = h (v - v_0)$ Hence, it depends on the frequency and not on the intensity of the incident radiation.