The sky looks blue due to the Mie scattering phenomenon, where the red colour has a large wavelength and doesn't get scattered as much. This same principle applies to signal scattering through optical fibers.
Mie Scattering
This type of scattering is based on Maxwell's equation and occurs when the size of the particle is larger than the wavelength of light. It's an elastic type of scattering, where the energy of the light remains unchanged. The sky appears blue and clouds appear white due to this type of scattering.
Electromagnetic Scattering
Electromagnetic scattering is a common phenomenon where electromagnetic waves get deflected continuously. There are two types of electromagnetic scattering: elastic and inelastic.
Elastic Scattering
This type of scattering includes Rayleigh and Mie scattering, while Raman and Compton's scattering are types of inelastic scattering.
The Factors that Affect Light Scattering
The size of the molecule or particle by which the light is scattered
• The wavelength of the incident light
If the wavelength of the incident light has a shorter wavelength and higher frequency (like blue light), it gets scattered more. On the other hand, if the wavelength is larger and the frequency is lower (like red light), it's deflected less.
The probability of scattering of light is inversely proportional to the fourth power of the wavelength:
p ∝ 1/λ4
Where p is the probability of scattering of light and λ is the wavelength of the light. This equation shows that the probability of scattered light is higher for shorter wavelengths.
Applications of Light Scattering
Light scattering has a wide range of applications, including:
- The sky appears blue as the light gets scattered by particles in the atmosphere.
- During sunset and sunrise, the sky appears red due to the scattering of light.
- In projectors
- In medical applications
- Provides an account of size, shape, number, and time independence of physical uniformities.
- Used in determining critical phenomena.
- Helps in molecular weight determination.
- Plays a vital role in air pollution analysis.
- Gives an account of diffusion phenomena.
Why is the Clear Sky Blue? Why are the Clouds White?
The clear sky appears blue because of Rayleigh scattering, where light gets scattered faster by particles with sizes smaller than the wavelength of light. The blue colour oscillates faster due to its shorter wavelength and higher frequency. This is why the clear sky appears blue.
Clouds appear white due to Mie scattering. When light strikes large particles in the atmosphere, such as water droplets, all colours split equally and scatter in all directions, giving rise to white light.
Exact Computational Methods
There are two types of exact computational methods: finite-difference time-domain (FDTD) method and T-matrix (null field method).
Finite-Difference Time-Domain Method (FDTD)
This method uses grid-based differential time-domain numerical modeling. The finite differential equation is solved using software or hardware in a leapfrog manner.
T-Matrix (Null Field Method)
This method, also known as the Extended Boundary Technique Method (EBTM), matches boundary conditions by Maxwell's equations. The incident transmitted and scattering fields are expanded into spherical vector wave functions.
Computational Approximation
There are two major categories of computational approximations: Mie approximation and discrete dipole approximation.
Mie Approximation
This is a completely analytical-based solution to Maxwell's equation for the scattering of electromagnetic radiation by spherical particles. It was formulated by Bohren and Huffman in 1998.
Discrete Dipole Approximation (DDA)
This method approximates continuous targets as a finite array of polarizable points. DDA courses are used to calculate DDA approximation to calculate light scattering particles.———-, this article has discussed the various types of light scattering and its applications in natural phenomena. Understanding the principles behind these phenomena can help us develop our concepts and appreciate the beauty of nature.