ATMOSPHERICAL OPTICS!
Mirages are due to the fact
that the index of refraction in hot air is considerably less
than the index of refraction in cool air.
Because the air is denser
closer to the surface, objects near the horizon appear much
higher in the sky than they actually are. The sun is still
visible after it sets, for example. For objects with as large an
apparent size as the sun and moon, the bottom of the image
"looms" higher than the top, so the circular disk appears
squashed.
Individual molecules scatter higher
frequencies of light with greater and greater intensity, so that
the open sky appears blue. However, small particles scatter all
frequencies of light with equal intensity, so that clouds of
water drops appear white. Fog is just a cloud at ground level.
Because when we view the setting sun or moon we view it through
the densest part of the atmosphere, almost all higher
frequencies are scattered out so we see only the lowest, reddest
frequencies.
Lord Rayleigh (1842 - 1919)
|
Gustav Mie (1868 - 1957) |
On Mars, the sky is pale pink,
and the sunset or sunrise are blue! Why?
Why does the eclipsed moon
turn some shade of red during a total lunar eclipse? It's lit
by all the sunrises and sunsets taking place over the entire
earth at that moment!
Curved Mirrors!
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