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Chapter 16
Optical Phenomena
of the Atmosphere
basic properties of light:
•
•
•
•
reflection,
refraction,
diffraction, and
interference.
Law of Reflection
• when light rays are reflected, they bounce
off the reflecting surface at the same
angle (the angle of reflection) at which
they meet that surface (the angle of
incidence).
Law of Reflection
On Smooth
Surface
On Rough
Surface
Internal reflection
• when light that is traveling through a
transparent material, reaches the
opposite surface and reflects back into
the transparent material.
Refraction
• is the bending of light due to a change in
velocity as it passes obliquely from one
transparent medium to another.
Bending
of
Light
Refraction
The bending of light
• by refraction is responsible for such
common optical illusions as the apparent
displacement of the position of the stars,
Moon, and Sun.
Mirages
• are an optical effect of the atmosphere
caused by refraction when light passes
from air with one density into air with a
different density and the object appears
displaced from its true position.
Highway Mirage
Hot Air Below Cool Air –
Objects Appearing Upside Down
inferior mirage
• occurs when the image appears below the
true location of the observed object.
• End day 1 notes.
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Cool Air Below Warm Air –
Objects Appear Above Their Positions
Looming
• When objects appear to be suspended
above the horizon.
• Looming is considered a superior mirage
because the image is seen above its true
position
Apparent Displacement of Position of the Sun
Towering
• Is a mirage that changes the apparent
size of an object.
Fata Morgana
• A type of towering that is observed in
coastal areas as towering castles that
appear out of thin air.
Rainbows
• Require sunlight and water droplets.
• the observer must be between the Sun
and rain
• water droplets act as prisms and
refraction disperses the sunlight into the
spectrum of colors, a process called
dispersion.
Formation
of a
Rainbow
Primary rainbow
• sunlight is reflected once within a
raindrop.
• In a secondary rainbow, light is reflected
twice within a raindrop before it exits.
The Visible Spectrum
Rainbow
Secondary
Rainbow
Halo
• is a narrow whitish ring with a large
diameter centered on the Sun.
• are produced by dispersion of sunlight
from atmospheric ice crystals that refract
light.
• End day #2 notes
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Common
Ice-Crystal
Configurations
Path
Taken
by Light
to Generate
Halos
Halo Produced by Dispersion
of Sunlight by Cirrostratus Clouds
sun dogs or parhelia
• mock suns.
• viewed near sunset or sunrise, is a
vertical shaft of light that appears to
extend upward from the Sun
Sun Dogs (Parhelia)
Sun Pillar
Glory
• commonly seen by pilots,
• consists of one or more colored rings that
surround the airplane’s shadow projected
on the clouds below.
corona
• a bright whitish disk centered on the
Moon or Sun.
• produced when water droplets scatter
light from the illuminating body.
The Corona
The Glory
diffraction
• bending of light as it passes near the
edges of cloud droplets.
• diffracted light will be directed into the
“shadow” of the droplet.
Multiple Distorted Images of Sun
Form a Long, Narrow Band
Chapter 16
END
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