A certain metallic surface is illuminated with monochromatic light of wavelength, . The stopping potential for photo-electric current for this light is 3V0. If the same surface is illuminated with light of wavelength , the stopping potential is V0. The threshold wavelength for this surface for photo-electric effect is:
Stopping Potential /Cut-off Potential -
It is defined as the potential necessary to stop any electron from reaching the other side.
Conservation of energy -
From equation (1) and (3)
if threshold wavelength is then