Reflection

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Reflection

</dt>
The process whereby a surface of discontinuity turns back a portion of the incident radiation into the medium through which the radiation approached. See albedo, reflectivity, radar reflectivity. </dd>
For true reflection to occur there must be a real discontinuity of the index of refraction or at least it must change over an interfacial layer of thickness small compared to the wavelength of the radiation. If the change of refractive index is gradual (as may occur in a stratified medium) radiation may be returned by a process of continuous refraction, not to be confused with reflection. In radar, the term reflection is often applied to the return of radio energy from a volume of precipitation or cloud particles, where scattering is the important process. When the scale of the irregularities on the reflecting surface is small compared to the wavelength, regular or specular reflection (also called mirror reflection, regual reflection) results; if the irregularities are large compare of reflection is not affected by wavelength except as the relative scale of the irregularities of the surface change with wavelength. the fraction of the incident radiation reflected does depend on wavelength because of the selective nature of the absorptivity and transmissivity. The idealized white body is a total reflector; a black body reflects none of the incident radiation. The laws of specular reflection are: (first law) the reflected ray lies in the same plane as the incident ray and the normal to the surface at the point of incidence; and (second law) the angle of reflection equals the angle of incidence, both measured from the normal to the surface. [[/a>|/a> ]]

References

This article is based on NASA's Dictionary of Technical Terms for Aerospace Use