Optical Phenomena - Bowmanville High School

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How light can trick us
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Apparent depth
Flattened sun and sunsets
Mirages
Shimmering
Rainbows
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The depth that an object appears to be due to the
refraction of light in a transparent medium
Eg. Looking into water from above
Light will refract away from the normal travelling
from water into air because air is faster
Our brains don’t acknowledge that the light is
refracted, so we extend the refracted ray straight
back, creating a virtual source of the light rays
OBJECTS IN WATER APPEAR
CLOSER TO THE SURFACE
PENCIL IN WATER APPEARS
BENT
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When the sun nears the horizon, it appears to be
flattened during a sunset
Light from the bottom of the sun is refracted more
than light from the top
This is because the air lower in the atmosphere is
more dense, slowing the light more
Rays from the bottom of the Sun have a greater
angle of incidence
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A virtual image that forms as a result of refraction
and total internal reflection in Earth’s atmosphere
This is the result of light travelling through
different air temperatures
The index of refraction decreases as air gets
warmer, causing the light to bend farther away
from the normal
Total internal reflection occurs in the hottest layer,
usually on the Earth’s surface
The ray travels back through to the cooler air and
bends back toward the normal
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When the light reaches our eyes, we think it
travelled in a straight line
This results in an image of the sky appearing to be
on the pavement or sand
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Also caused by light refracting through different air
temperatures
Air closer to the lake is warmer, so the light refracts
in the same pattern as it does near hot pavement
Total internal refraction occurs in the lowest,
warmest layer causing multiple virtual images on
the water’s surface
Rainbows are a result of the dispersion of white
light into its 7 colour components
 Remember: red light is refracted less than violet
due to its speed
ROYGBIV
 Rainbows are produced by water droplets
3 steps:
Dispersion of white light by the rain drop
Partial internal reflection at the back of the rain drop
Refraction of the light exiting the rain drop
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Our eyes see the final refraction, and projects
these rays backwards to form a virtual image of a
rainbow
You can only see a rainbow when the sun is behind
you
Apparent Depth
http://wpcontent.answers.com/wikipedia/commons/6/62/
Pencil_in_a_bowl_of_water.png
Water Mirages
http://img2.blogabond.com/UserPhotos/1937/580/Water
Mirage.jpg
http://www.kookynet.net/media/k3832_p-miragesimpson.jpg
Mirage Diagram
http://image.tutorvista.com/content/lightrefraction/mirage.jpeg
Moon shimmering
http://www.boatnerd.com/news/newsthumbs/images
/Moon-10-25-04-dcr.jpg
http://jamminwithjay.com/images/080612_alaska/Ala
ska_074.JPG
Rainbow
http://www.alaska-inpictures.com/data/media/13/rainbow-over-themuldrow-glacier_1127.jpg
http://www.rebeccapaton.net/rainbows/formatn.htm

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