__Plank Quantum Theory : __

In 1900 a German physicist Max Plank presented his theory about light, called plank quantum theory. This theory has the following postulates: -

(1) Light is not emitted or absorbed continuously.

Light is emitted or absorbed in the form of packets of energies, which are called photon or quantas.

2; Each packet is associated with definite amount of energy , which is directly proportional to fhe frequency of radiation.

E = hn nis the frequency and h is plank constant

3; This is called plank equation and h is plank constant the value of which is 6.626x 10^{-34 }Jsec

4; The energy emitted or absorbed by a body is always whole number multiple of quantum . i.e. E_{n} = n hn