In 1900, Max Planck proposed the quantum theory to explain the emission and absorption of radiations. Heated objects give off these radiations. According to his revolutionary hypothesis, energy travels in a discontinuous manner and is composed of a large number of tiny discrete units called quanta.
Main postulates of Plank’s Quantum Theory:
The main points of the theory are:
1. Energy is not emitted or absorbed continuously. Each wave packet or quantum is associated with a definite amount of energy. In the case of light, the quantum of energy is often called the photon.
2. The amount of energy associated with a quantum of radiation is proportional to the frequency of the radiation.
Ε ∝ ∨
Where ‘h’ is a constant known as Planck’s constant and it is equal to 6.625X10-34 Joule sec.
3. A body can emit or absorb energy only in terms of integral multiples of a quantum.
E = n h ∨
n= 1, 2, 3… (Integral Multiple)
The frequency ‘∨’ is related to the wavelength ‘λ’ of the photon as.
∨ = c/λ.
E = h c/λ