Chapter 15: Light,
color and
atmospheric optics
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White and colors
White clouds and scattered light
Blue skies and hazy days
Red suns and blue moons
Twinkling, twilight, and the green flash
The mirage: seeing is not believing
Halos, sundogs, and sun pillars
Rainbows
Coronas and cloud iridescence
White and colors
White and colors
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review of fate of visible light passing
through the atmosphere
review of relationship between wavelength
and colors
White clouds and
scattered light
White clouds and scattered
light
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reflection
scattering
• Thunderstorms appear dark because the clouds
(cumulonimbus) are about 10 km deep, scattering
most of the light.
Blue skies and hazy
days
Blue skies and hazy days
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selective scattering
effect of scattering particle size
crepuscular rays
Red suns and blue
moons
Red suns and blue moons
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path length of sunlight passing through the
atmosphere
atmospheric particle effects
• The “definition” of a blue moon as two full moons in
a single calendar month has nothing to do with
atmospheric optics.
The mirage: seeing is
not believing
The mirage: seeing is not
believing
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inferior mirage
superior mirage
• Mirages are very common and may be seen frequently
if you look for them.
Inferior mirage
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warm surface, decreasing temperatures
aloft
• The proper conditions for an inferior mirage are commonly
found over a hot road surface during summer, or over
an unfrozen lake on a very cold day.
Superior mirage
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cold surface, warmer temperature aloft
• The proper conditions for a superior mirage are commonly
found over water and over snow-covered surfaces.
Fata morgana
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complex vertical temperature profile
• According to legend, King Arthur’s half-sister,
Fata Morgana in Italian, was a fairy enchantress
trained by Merlin the Magician. She lived in a crystal
palace beneath the water and could build fantastic
castles from thin air.
Halos, sundogs, and
sun pillars
Halos
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ice crystals
dispersion
• Halo-producing ice crystals are commonly found
in cirrostratus clouds
Sundogs
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hexagonal ice crystals
horizontal orientation
• Sundogs are commonly seen when cirrostratus clouds
are in the sky.
Sun pillars
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reflection phenomenon
• Sun pillars can be seen shortly after sunrise or
shortly before sunset on very cold days.
Rainbows
Rainbows
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water droplet phenomenon
reflection and dispersion
necessary conditions for a rainbow
the primary rainbow
The secondary rainbow
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two internal reflections
• A tertiary rainbow also exists, but it is too faint to
be seen with the human eye.
Coronas and cloud
iridescence
Coronas and cloud
iridescence
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diffraction
The corona
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necessary conditions
Cloud iridescence
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another water droplet diffraction
phenomenon
The Glory
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necessary conditions for viewing
• It is very common to see a glory from the window
of an airplane. Make sure you are sitting on the
side opposite the sun.