# Plank’s Quantum Theory of Radiations

## Plank’s Quantum Theory of Radiations:

In 1900, a German Physicist Max Plank had studied radiations emitted by hot black body and proposed quantum theory of radiations.

## Main Postulates of Plank’s Quantum Theory of Radiations:

Postulates of the theory are:

1. Energy radiated by hot bodies is not continuous, rather it is emitted in the form of “energy packets” or “energy pulse” known as quanta (singular is quantum). The particle of energy (radiations) is also called photon.
2. Each quantum has a definite amount of energy. This energy of the quantum is directly proportional to frequency of radiations.

E  ∝   ﬠ

Or

E = h ﬠ

1. According to Plank, energy of a quantum or photon is given as:

E= h ﬠ

Where  E = energy

h = Plank’s constant

= 6.6262 x 10-34 J.s

But      ﬠ          =        c / λ

So        E          =        hc / λ

Equation-1 shows that energy is directly proportional to frequency of radiations.

E  ∝   ﬠ

While equation-2 shows that energy is inversely proportional to wave length.

E  ∝   1 / λ

1. The energy emitted or absorbed by a body is always whole number multiple of quantum i.e.  En = n h ﬠ    where n = 1, 2, 3,……..

This means energy is quantized.

Energy of photon can also be given as:

_

E = hc

In 1905, Einstein also gave similar idea of particle nature of radiations.

He gave equation :

E = mc2

### 1 thought on “Plank’s Quantum Theory of Radiations”

1. Hey there I am so thrilled I found your weblog, I really found you by error, while I was browsing on Digg for something else, Regardless I am here now and would just like to say thanks for a marvelous post and a all round enjoyable blog (I also love the theme/design), I don’t have time to browse it all at the minute but I have saved it and also included your RSS feeds, so when I have time I will be back to read a great deal more, Please do keep up the superb work.