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## PowerPoint Slideshow about ' Light Scattering' - annick

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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
- 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

- 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

- 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

- 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

- 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…)

- 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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