The graph of Fig. shows the variation of photoelectric current (I) versus applied voltage (V) for the two different photosensitive materials for two different intensities of the incident radiation. Identify the pairs of curves that correspond to different materials but same intensity of incident radiation.

Explanation

Curves 1 and 2 correspond to similar materials while curves 3 and 4 represent different materials, since the value of stopping potential for the pair of curves 1 and 2 and 3 and 4 are the same. For given frequency of the incident radiation the stopping potential is independent of its intensity.
So, the pairs of curves (1, 3) and (2, 4) correspond to different materials but same intensity of incident radiation.