Question

Define stopping potential (cut-off potential) with reference to photoelectric effect.

Answer 1

Hint: To answer this question, we first need to understand what is potential. The chemical potential of a species is the energy that can be absorbed or released owing to a change in the particle number of the given species, for as in a chemical reaction or phase transition, according to thermodynamics.

Complete step-by-step solution:
Photoelectric effect – When a substance absorbs electromagnetic radiation, electrically charged particles are emitted from or within it, causing the photoelectric effect. The ejection of electrons from a metal plate when light falls on it is a common definition of the effect. The radiant energy may be infrared, visible, or ultraviolet light, X-rays, or gamma rays; the substance could be a solid, liquid, or gas; and the released particles could be ions (electrically charged atoms or molecules) or electrons.
Stopping potential - The needed potential for preventing the removal of an electron from a metal surface when the incident light energy is larger than the work potential of the metal on which the incident light is focused is known as the stopping potential or cut-off potential.
The strength of incident radiation has no bearing on the stopping potential. The value of saturated current rises as the intensity rises, but the stopping potential remains constant.
The stopping potential for a given intensity of radiation is determined by the frequency. The value of stopping potential increases as the frequency of incident light increases.
So, we conclude that, stopping potential or cut-off potential is the negative potential of the collector plate at which the photoelectric current becomes zero. Stopping potential is the difference in retarding potential between two plates that is just enough to stop the highest energetic photoelectrons from being released.

Note: Heinrich Rudolf Hertz, a German physicist, developed the photoelectric phenomenon in 1887. Hertz discovered that when ultraviolet light shines on two metal electrodes with a voltage put across them, the voltage at which sparking occurs changes. This was related to his work on radio waves.