Question:
Why does the color Black absorb heat and White reflect heat? What
are the physical properties behind this fact? I have seen some Arabs where
Black robes in the desert -- this seems to defeat the purpose. Do they wear
them because black protects more against harmful UV rays?
Replies:
First of all I have no idea why some Arabs wear black robes in
the desert. It seems counter-productive...but oh well, different strokes for
different folks. Anyway, the color that we observe (i.e. the color of a
particular object) is really only the light that is reflected from that
object. For example, a red ball appears red because when white light strikes
it, all of the light is absorbed except for the red frequencies/wavelengths
which are reflected into our eyes. A white light is made up of all visible
(and invisible) wavelengths all mixed together. So an object that appears
white, is reflecting all of the incident wavelengths and absorbing nothing (or
very little). A black object, on the other hand is absorbing all of the
incident wavelengths (along with all of their energies) which causes it to
heat up. That is why snow does not melt in cold weather even when the sun is
falling directly on it. All of the incident light energy is reflected away
and none (or very little) is absorbed.
Unknown
Up-date July 2001
The explanation I heard for this is that the clothes themselves are
very loose (rather like Roman togas). The extra heat caused by the
black colour causes increased upward convection of the air between
the cloth and their body. This additional air circulation actually aids in
evaporation of persiration and thus results in better cooling.
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