# Why Black Body Radiation is Really Useful To Physics?

Classical physics was unable to explain phenomena such as atomic spectra, blackbody radiation, the photoelectric effect, the Compton effect, and solid specific heat capacity.

The inadequacy of the Rayleigh-Jeans formula to describe the known energy distribution of black body radiation indicated that something was wrong with the equipartition law, classical electromagnetic theory, or both.

The shortcomings of classical mechanics prompted the creation of Quantum Mechanics, the Birth of the quantum theory, and Black body radiation. Max Planck of Germany brought quantum theory to physics in the year 1900 while attempting to explain the observed energy distribution of the electromagnetic radiation generated by a black body.

He postulated that the atoms in the walls of the blackbody (cavity) operate similar to micro electromagnetic oscillators, each having a unique frequency of vibration. Furthermore, an oscillator generates and absorbs electromagnetic waves of identical frequency.

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Two assumptions are made in his hypothesis concerning the atomic oscillations that are in equilibrium with electromagnetic radiation inside the cavity.

1. An oscillator can have a discrete set of energies which are integral multiples of finite quantum of energy E = hν where h is a universal constant called Planck’s constant (h = 6.626 x 10-34 Js and ν is the frequency of the oscillator. Thus, the energy of the oscillator can only have the values E = nhν where n = 0,1,2,3,4 ………. called quantum numbers.

2. The change in energy of the oscillator can take place due to emission or absorption of radiation (of discrete energy hν) only when an oscillator jumps from one energy state to another.

According to the postulate of Plank, the oscillators can exist in a set of discrete energy states 0, hν, 2hν, 3hν, 4hν, etc.

## SIGNUP FOR MORE INTERESTING AND EXCITING NEW CONTENT

• THERMODYNAMICS
It is the branch of physics that deals with the concepts of heat and temperature and the inter conversion of heat and other forms of energy.
• THERMAL PROPERTIES OF MATTER
Temperature is a relative measure or indication of the hotness or coldness of a body. The temperature of a body determines the direction of the flow of energy. The SI unit of temperature is kelvin (K). °C is a commonly used unit of temperature.
• MECHANICAL PROPERTIES OF FLUIDS – PART 2
The viscous drag increases with increases velocity of the body, but it is found that the body after attaining certain velocity starts moving with a constant velocity called terminal velocity.
• MECHANICAL PROPERTIES OF FLUIDS – PART 1
The materials that can flow are called fluids. Liquids and gases are collectively known as fluids. Unlike a solid, a fluid has no definite shape of its own.
• MECHANICAL PROPERTIES OF SOLIDS
The property of a body, due to which it tends to regain its original size and shape when deforming force is removed, is called elasticity. The deformation caused is called as elastic deformation.

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