Question

The graph shows variation of stopping potential $V_0$ versus frequency of incident radiation for two photosensitive metals A and B. Which of the two metals has higher threshold frequency and why?

Answer 1

Metal A has high threshold frequency. The threshold frequency is defined as the minimum frequency of incident light which can cause photo electric emission ie, this frequency is just able to eject electrons without giving them additional energy. Also stopping potential is the potential necessary to stop any electron from reaching the outside. As the frequency increases stopping potential also increases. At zero stopping potential the frequency of incident radiation is more to metal A. Both the metals have same stopping potential at different frequency and this frequency is more than metal A. So metal A has higher threshold frequency.