Reflection
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Reflection
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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.
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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