The graph of Fig. shows the variation of photoelectric current with collector plate potential for different frequencies of incident radiations.

(i) Which physical parameter is kept constant for the three curves?
(ii) Which frequency `(v_1,v_2 or v_3)` is the highest?

Explanation

(i) Since the saturation current is same for all the three curves, so the intensity of the incident radiation is same for all the three radiation.
(ii) From graph, the value of stopping potential is highest for the radiation of frequency `v_1`, so the frequency `v_1` is highest.