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Explain This
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The Physics of the Human Eye
![image of Eye on retina](exp_human027.jpg)
Graphic from
dorling kindersley books
website
Video Instruction
showmethephysics.com
Fill In the Blank Notes
D. Index of Refraction (n)
– a comparison of speed of light in a substance to its speed in a vacuum
![](watertank.jpg)
If a substance has an index of refraction of 2.00 it means light is
twice as fast
in a vacuum than it is in that medium
c = speed of light in a vacuum
(3.00 x 108
m/s)
v = speed of light in a medium
![](imgDD.gif)
nvacuum = 1.00
nair
≈ 1.00 , v
≈ 3 x 108 m/s
Which substance slows down light
the most when light enters from air?
Diamond,
(highest (n) index of refraction)
least?
Water
(smallest (n) index of refraction)
Any device with a lens refracts light
Ex 1) Speed of light in alcohol?
n = 1.36
(Reference Table)
n = 1.36 = c/v
1.36 =
(3.00 x 108
m/s)/V
3.00 x 108
m/s = 1.36V
V = 2.21 x
108 m/s
Magnifying glasses enlarge objects with
refraction
![](magnifier750.jpg)
http://www.freeimages.co.uk/
n & v relationship?
n = c/v
Inverse
The more light is
slowed down
or sped up,
the more
it changes direction
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Refraction in Glass
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The human eye refracts light
1. Prediction θref from θin
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a. Snell's Law
1 – incident medium
2 – refractive medium
Air/Lucite
n1sinθ1 = n2sinθ2
1.00 sin53 = (1.50) sinθ2
.798 = 1.50sinθ2
.798/1.50 = sinθ2
.532 = sinθ2
(inverse sine .532)
θ2 = 320
Ex) Light refracts as it moves
from water to flint glass. Which
angle is bigger, qin
or qref?
Faster medium has bigger angle
Water 1.33?? or Flint glass 1.66??
Angle of Incidence bigger, Water faster
Ranking
Task
Rank the media below from
fastest to slowest
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Fooling Drinkers With Refraction
More
Refraction Equation Instruction
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Enrichment
NOVA (PBS) explains
how refraction makes diamonds sparkle
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