Transcript The mirage
Chapter 15: Light,
color and
atmospheric optics
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
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
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
selective scattering
effect of scattering particle size
crepuscular rays
Red suns and blue
moons
Red suns and blue moons
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
inferior mirage
superior mirage
• Mirages are very common and may be seen frequently
if you look for them.
Inferior mirage
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
cold surface, warmer temperature aloft
• The proper conditions for a superior mirage are commonly
found over water and over snow-covered surfaces.
Fata morgana
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
ice crystals
dispersion
• Halo-producing ice crystals are commonly found
in cirrostratus clouds
Sundogs
hexagonal ice crystals
horizontal orientation
• Sundogs are commonly seen when cirrostratus clouds
are in the sky.
Sun pillars
reflection phenomenon
• Sun pillars can be seen shortly after sunrise or
shortly before sunset on very cold days.
Rainbows
Rainbows
water droplet phenomenon
reflection and dispersion
necessary conditions for a rainbow
the primary rainbow
The secondary rainbow
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
diffraction
The corona
necessary conditions
Cloud iridescence
another water droplet diffraction
phenomenon
The Glory
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.