Publication Year

2001

Keywords

Light, spherical particles, physics, chemistry, Mie

Disciplines

Atomic, Molecular and Optical Physics | Chemistry | Physical Sciences and Mathematics | Physics

Abstract

The phenomenon of light scattering in the sky is observable in everyday life. When light energy encounters a particle it causes it to reradiate light in all directions. This phenomenon of light deflection is known as scattering. If the particle is smaller than the wavelength of the light, λ , the probability of this scattering is proportional to 1/λ4. Hence, blue light, which is a t the short wavelength end of the visible spectrum, will be scattered much more strongly than will the long wavelengths of red light. This results in the blue color of the sky, since, from directions other than toward the sun, the observer sees only scattered light. At sunset, in the direction of the sun, red light is seen, because these long wavelengths get through to the observer's eyes with very little scattering. Therefore, light scattering by particles and molecules in the atmosphere gives rise to the blue color of the sky and the beautiful red colors that can be seen at sunrise and sunset. This was one of the earliest examples of scattering and was studied by Lord Rayleigh in the 1870's. Today, this type of scattering is known as Rayleigh scattering. For larger particles, Mie theory must be used. These types of scattering are subsequently discussed in detail.

Department 1 Awarding Honors Status

Physics

Department 2 Awarding Honors Status

Chemistry

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