Question

What is photoelectric effect? Give Einsteins explanation of the phenomenon.

Answer 1

Photoelectric Effect:

The phenomenon of emission of electrons from metal surface when exposed to light energy of a suitable frequency is known as photoelectric effect.

Einstein’s Explanation:

As per Einstein, an incident photon having energy $h\nu$ ejects electron from a metal having work function $W=h{\nu }_0$ and imparts kinetic energy K.E. $=\frac{1}{2}m{v}^2$ to it.

Einstein proposed a theory in 1905 to explain photoelectric effect.

When a photon of energy $h\nu$ falls on a metal surface , its energy is used in 2 ways.

1.A part of energy is used to liberate electron from the metal surface. This is called $W$ workfunction.

2.The remaining energy is used to impart kinetic energy of electron.

$h\nu =W+\frac{1}{2}m{v}^2$

When $\nu ={\nu }_0$ ,K.E = 0;

Then eq. will become $h{\nu }_0=W$

Substituting,

$h\nu -h{\nu }_0=\frac{1}{2}m{v}^2$

This is Einstein’s photoelectric equation.