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The Physics of the Human Eye

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

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

n_vacuum = 1.00  

n_air ≈ 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

http://www.freeimages.co.uk/

 n & v relationship?

n = c/v

Inverse

Refraction in Glass

The human eye refracts light

1. Prediction θ_ref from θ_in

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, q_in or q_ref?

Faster medium has bigger angle

Water 1.33?? or Flint glass 1.66??

Angle of Incidence bigger, Water faster

Fooling Drinkers With Refraction

More Refraction Equation Instruction

Refraction Relationships

Enrichment

NOVA (PBS) explains how refraction makes diamonds sparkle

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