Question

The stopping potential for a photo cell depends

• A. On the nature of the cathode and intensity of light
• B. On both the intensity and frequency of incident light
• C. Only on the intensity of light
• D. On both the nature of the cathode and frequency of incident light

Answer 1

The correct option is D On both the nature of the cathode and frequency of incident light

It is known that the stopping potential of a metal is the potential required to stop the fastest electron emitted from its surface due to the photoelectric effect.

If $q_e$ is the charge on the electron and $V_o$ is the stopping potential, then we have

$q_e{V}_o=K_{max}$

where $K_{max}$ is the maximum kinetic energy of the emitted electrons.

Recalling the photoelectric effect, we know that

$K_{max}=h(f-f_o)$

where $h{f}_o$ is the work function of the metal and $f_o$ is its threshold frequency. From the above two equations, it can be observed that the stopping potential of a metal depends on:

(i) frequency $f$ of the incident light and

(ii) work function which in turn means the nature of the cathode (metal).