Light scattering
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Light Scattering. Rayleigh Scattering & Mie Scattering. What is Scattering?. Process by which particles suspended in a medium of a different index of refraction diffuse a portion of the incident radiation in all directions

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Presentation Transcript
Light scattering

Light Scattering

Rayleigh Scattering & Mie Scattering


What is scattering
What is Scattering?

  • Process by which particles suspended in a medium of a different index of refraction diffuse a portion of the incident radiation in all directions

  • No energy transformation results, only a change in the spatial distribution of the radiation

  • Function of ratio of particle diameter to wavelength of incident radiation


Scattering plane
Scattering Plane

  • Defined by the two rays involved, the source-particle ray and the particle-observer ray

  • Determined by observation, not fixed in space. For example, if the observer moves, the scattering plane will move with the observer.


Rayleigh scattering
Rayleigh Scattering

  • Particles much smaller than wavelength of radiation

  • Proportional to 1/ λ4

  • Shorter wavelengths scattered much more than longer wavelengths

  • Air molecules (N2 and O2) just the right size to very effectively scatter the shorter wavelengths (blue light) of incident solar radiation => blue sky


Mie scattering
Mie Scattering

  • Scattering by a isotropic, homogeneous sphere

  • Particle dimension comparable to wavelength of radiation (aerosols, water vapour)

  • Longer wavelengths scattered more than shorter wavelengths

  • More forward scattering

  • Scattering properties depend on wavelength, size, real and imaginary parts of refractive index, and size distribution





Theory
Theory

  • Fundamental Equation of RT

  • Phase Function Expansion

  • Can use addition theorem for spherical harmonics to expand P in Fourier cosine series over azimuthal angle


Theory contd
Theory (Contd…)

  • Expand I in Fourier cosine series

  • RT equation transformed into 2M independent integro-differential equations

  • Integration performed by Gaussian quadrature (2N ‘streams’)

  • Reference: http://www.gps.caltech.edu/~vijay/Papers/RT_Models/DISORT%20Report.pdf


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