The Fig shows a plot of three curves a, b, c showing the variation of photocurrent versis collector plate potential for the different intensities `I_1, I_2 and I_3` having frequencies `v_1, v_2 and v_3` respectively, incident on a photosensitive surface. Point out the two curves for which the incident radiation have same frequency but different intensities.

Explanation

Since the value of stopping potential is same for curves a and b and have different saturation current, hence frequency `v_1 and v_2` are the same but their intensities are different.