Download Atmospheric Phenomena Hexagonal Ice Crystals Fall Flat Sub Sun

Atmospheric Phenomena
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Hexagonal Ice Crystals
Fall Flat
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Sub Sun
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Sub Suns
Sun Pillars
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Sun Pillar
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Multiple Reflections
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Corner Cubes
Clicker Question
Things appear black because they absorb all
the colors of the spectrum. Then why does
glossy black paint look shiny, and flat black
paint doesn’t?
1. It is an optical illusion.
2. The glossy paint is smoother than the flat
paint.
3. The paints are actually not black - they just
look that way.
4. Glossy paint has a clear shiny outer layer.
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Diffuse Reflections
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Specular vs. Diffuse
• Specular obeys law of reflection
• Diffuse does not (except
microscopically)
Wet pavement
• Examples – Paper
– Movie theater screen
– Dry pavement
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Refraction
Refraction
Reflection
Incoming
• recall: when a wave enters a medium
where the speed changes, some is
reflected
• the angle of the transmitted portion is
changed - this is refraction
_refraction
Refraction
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Index of refraction
Law of refraction
• Index of the refraction, n, is defined as
n = c/v v: velocity of light in medium
• Examples
– Vacuum
– Air
– Water
– Glass
– Diamond
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n=1
n = 1.0003
n = 1.33
n = 1.5
n = 2.4
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• When light goes from a medium with
smaller index of refraction to a medium
with larger index of refraction, it bends
toward the normal.
• When light goes from a medium with
larger index of refraction to a medium
with smaller index of refraction, it bends
away from the normal.
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Air
Snell’s Law
Water
ni Sinθi = nf Sinθf
• From air to water, θair = 30ο then θwater= 22ο
_r
Water
• From water to air, if θwater= 22ο , then θair = 30ο ,
_r
Air
or if θwater = 30ο then θair = 42ο
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Straw illusion:
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Spear fishing
A straight straw
appears to have
bent in water
due to refraction.
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Spear-fishing is made more
difficult by the bending of light.
To spear the fish in the figure,
one must aim at a spot in front of the fish
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