Scattering of electromagnetic radiation

The scattering of electromagnetic radiation refers to the process by which electromagnetic waves deviate from their original path due to interactions with particles or obstacles in their path. This phenomenon is fundamental to understanding various natural phenomena and is crucial in fields such as optics, atmospheric science, and astronomy. There are different types of scattering, including Rayleigh scattering, Mie scattering, and Raman scattering, each occurring under specific conditions and involving different mechanisms.

1. Rayleigh Scattering:

   • Description: Rayleigh scattering occurs when the size of the scattering particles is much smaller than the wavelength of the incident radiation. It is inversely proportional to the fourth power of the wavelength, meaning shorter wavelengths (blue light) scatter more easily than longer wavelengths (red light).

   • Application: Rayleigh scattering is responsible for the blue color of the sky during the day. It is also a significant factor in the scattering of sunlight in the Earth's atmosphere.

2. Mie Scattering:

   • Description: Mie scattering occurs when the size of the scattering particles is comparable to the wavelength of the incident radiation. Unlike Rayleigh scattering, Mie scattering is less dependent on wavelength.

   • Application: Mie scattering is often observed in the atmosphere when there are larger particles such as dust, water droplets, or ice crystals. It plays a role in phenomena like halo formations around the sun or moon.

3. Raman Scattering:

   • Description: Raman scattering involves a change in the energy of the scattered photons. When incident photons interact with molecules, they can transfer energy to or receive energy from the molecules, leading to a shift in the scattered wavelength.

   • Application: Raman spectroscopy is a technique that uses Raman scattering to study vibrational, rotational, and other low-frequency modes in a system. It has applications in chemistry, biology, and materials science.

4. Brillouin Scattering:

   • Description: Similar to Raman scattering, Brillouin scattering involves a change in the energy of the scattered photons. However, Brillouin scattering is associated with the interaction of light and acoustic phonons (lattice vibrations) in materials.

   • Application: Brillouin scattering is used in Brillouin spectroscopy to measure the mechanical properties of materials, such as their elastic constants and sound velocities.

dP_scatt = W_scatt dS

= energy/time

= power

dΩ = solid angle = dS/r²

dPscatt/ dΩ = W_scatt dS/ dΩ = W_scatt r²

Pinc = intensity of incident radiation

d𝜎/ dΩ = Pscatt/ Pinc = ( Wscatt / Pin) r²

Total scattering cross section

𝜎 = ∫d𝜎/ dΩ dΩ

For free electron

Equation of motion is given as ma = eE

The solution of this equation is

Oscillating charge behave as dipole dipole moment

Intensity of scattered radiation

Total scattering cross section

Understanding the scattering of electromagnetic radiation is essential for interpreting experimental data, designing optical systems, and gaining insights into the properties of the scattering medium. It is a complex phenomenon influenced by factors such as wavelength, particle size, and the nature of the scattering medium.

This note is a part of the Physics Repository.