<p>The graph provided shows the variation of photoelectric current (I) with applied potential difference (V) for two photosensitive materials under illumination with radiations of the same frequency but different intensities.</p>

<p><img alt="" src="https://school.achievam.com/upload/questionbank/question/que_1759162415.jpg" style="height:120px; width:128px" />​​​​​​​</p>

<p>(a) From the graph, identify which pair of curves represents <em>different materials exposed to the same radiation</em>.</p>

<p>(b) From the same graph, determine which pair corresponds to <em>different materials but illuminated with the same intensity of incident light</em>.<br />
Justify your answers based on the characteristics of the graph.</p>