Atmospheric Optics
• Scattering
• Reflection
• Refraction
• Diffraction
The amazing variety of optical phenomena observed in the atmosphere can be explained by four physical mechanisms.
1
Refraction
• Green Flash
• Mirage
• Halo
• Tangent Arc
• Rainbow
2
Refraction
Light slows down as it passes from a less dense to a more
dense medium.
As light slows it bends toward the
denser medium. Similar to waves approaching a beach.
The amount of bending depends on the wavelength (color) of the
light, leading to dispersion or separation of colors.
3
Refraction in Air
Mirage
4
Refraction in Air
Mirage
5
Refraction in Air
Green Flash
6
7
Refraction in Air
Green Flash
8
Refraction in Air
Green Flash
9
Refraction in Air
Green Flash
10
Refraction in Air
Red Flash
11
Refraction by Ice Crystals
22 1/2˚ Halo
12
Refraction by Ice Crystals
Sun Dogs
13
Refraction by Ice Crystals
Sun Dog
14
Refraction by Ice Crystals
22 1/2˚ Halo
15
Refraction by Ice Crystals
22 1/2˚ Halo and Upper Tangent Arc
16
Refraction by Ice Crystals
22 1/2˚ Halo
17
Refraction by Ice Crystals
Halo Complex
18
Refraction by Ice Crystals
Halo Complex
19
Refraction by Ice Crystals
46˚ Halo?
20
Refraction by Ice Crystals
Lower Tangent Arc
21
Refraction by Ice Crystals
Lower Tangent Arc
22
Refraction and Scattering
Sun Pillar and Sun Dog?
23
Refraction by Water Drops
24
Refraction by Water Drops
25
Refraction by Rain
26
Refraction by Water Drops
Primary Rainbow
Violet
Red
27
Refraction by Rain
Double Rainbow
28
Refraction by Rain
Double Rainbow
29
Refraction by Rain
Partial Rainbow
30
Refraction by Rain
Double Rainbow
31
Refraction by Rain
High Sun: Low Rainbow
32
Refraction by Rain
Low Sun: High Rainbow
33
Refraction by Rain
! Rainbow seen from Airplane
34
Diffraction
Constructive interference of light waves can produce
color separation.
The physical mechanism in
this case is called diffraction.
Produces colors on soap
films, oil slicks, and music CDs.
35
Diffraction causes Interference
Diffraction is the tendency of light waves to bend as they pass the edges of objects.
36
Diffraction by Soap Film
Examples include:
• Iridescence
• Corona
• Glory
• Supernumerary bows
37
Diffraction by Cloud Drops
Iridescence
38
Diffraction by Airplane Window
Artificial Iridescence
39
Diffraction by Cloud Droplets
Corona
40
Diffraction by Pollen
Corona
41
Diffraction and Reflection
Glory
42
Diffraction and Reflection
Glory
43
Diffraction and Reflection
Glory
44
Diffraction and Reflection
Supernumerary Rays
45
Diffraction and Reflection
! Fog Bow: larger drops do not allow dispersion of colors.
46
Diffraction and Reflection
! Fog Bow: larger drops do not allow dispersion of colors.
47
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