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

The similar materials will have same stopping potential and the different materials will have different stopping potential whatever may be the intensity of incident radiation.
For the same intensity of two different incident radiations on two different materials, there will be same value of photoelectric current. So the pair of the curves (1 and 3) or (2and 4) correspond to different materials but having same intensity of incident radiations.