Question

A non-monochromatic light is used in an experiment on photo electric effect. The stopping potential is :

• A. Related to the mean wavelength
• B. Related to the longest wavelength
• C. Related to the shortest wavelength
• D. Not related to the wavelength

Answer 1

The correct option is D Not related to the wavelength

The stopping potential depends on the work function of the material.

The work function of a metal is given as

$K_{max}=\frac{hc}{\lambda }-\varphi$

The threshold wavelength occurs when$K_{max}=0$

Hence the stopping potential is not dependent on the wavelength of the light. The energy of the light source is greater and the kinetic energy of the ejected is also high and accordingly higher potential is required to stop the electron.