I am asking how wavelengths affect scattering(not diffraction). We know lesser the wavelength, greater is the scattering. For example, violet ray(wavelength 0.4 micron) is scattered most and red ray(wavelength 0.7 micron) is scattered the least among the visible light rays. But, I am asking WHY does this happen?

  • $\begingroup$ You need to look up Rayleigh scattering. $\endgroup$ – Farcher Feb 12 '16 at 13:29

Briefly: radiation is generated by accelerating charges. The acceleration of a charged system is equal to the second derivative of position w.r.t. time. An oscillating charge produces an oscillating field: a radiating wave. For a sinusoidally varying charge, the second derivative is proportional to the square of the frequency of the wave, so the intensity of the radiation is proportional to the frequency squared.

The process of exciting a charged system into a state of oscillation is the same process in reverse: an oscillating field produces an oscillating charge. The amplitude of the charge oscillation is proportional to the frequency squared.

For scattering, both mechanisms occur: The field excites the charges into oscillation, and the oscillating charge radiates. The effectiveness of the scattering is then proportional to the effectiveness of excitation multiplied by the effectiveness of the radiation, and is thus proportional to frequency to the fourth power. Higher frequecies (bluer light) is scattered more effectively than lower frequency light.


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