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# What is scattering of light?

Physics | 7-14 yrs | Interactive

Scattering is the phenomenon by which a beam of light is redirected in many different directions when it interacts with a particle of matter.

### What is the difference between scattering of light and just normal reflection?

Scattering occurs when a particle of light is fully absorbed and then emitted, while reflection is when a wave/particle is simply reflected off the surface without interacting.

### What is the difference between scattering of light and just normal refraction?

Refraction is the bending of light as it crosses different transparent/translucent mediums, and doesn’t experience any change except it bends. In scattering, light experiences a change in its properties.

## How does light scattering work?

When light experiences particles on its path, it is scattered by the particles, it encounters. The intensity of the scattered light depends on the size of the particles and the wavelength of the light.

## Light scattering theory

According to Rayleigh theory, a theoretical description of light scattering involving particles much smaller than the wavelength of the light, makes the sky blue.

When light meets a molecule smaller than its wavelength, the electric fields temporarily polarise the molecule, re-distributing the electrons in the molecule such that one end has a weak positive charge, and the other has a weak negative charge. This separation of charges is called a dipole moment. As the oscillating electric fields interact with the molecule, the molecule’s dipole moment oscillates and the molecule re-radiates the light in all directions.

Rayleigh scattering can be considered to be elastic scattering since the photon energies of the scattered photons do not change.

Molecules with larger sizes than the wavelength of the light , experience scatter differently. They experience what is known as the Mie Effect. Since the particles are bigger, the light appears white. This is why clouds, which are made of droplets of water appear white.

These principles are sometimes used to calculate molecular mass.

## Why do shorter wavelengths scatter more?

Shorter wavelengths and higher frequency scatter more because, the more wavy the line, the more chances it has of intersecting with a particle. Longer wavelengths have lower frequency and so have less chances as they are straighter and chances of colliding or intersecting with a particle is less.

### Why is the sky blue?

The colour of the sky is blue because of the shorter wavelength and the length of the path. The colour of the sky changes as the path distance changes.