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image of Eye on retina

Graphic from dorling kindersley books website

 

 

 

 

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

 

n = c/v

 

c = speed of light in a vacuum
(
3.00 x 108 m/s)

    v = speed of light in a medium

 

 

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

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

 
 
 

Refraction in Glass

 

 




The human eye refracts light

 

 

 

1. Prediction θref from θin


 

 



 

 

 

a. Snell's Law

n1sinθ1 = n2sinθ2

 

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

 

 

 

 

 

 

Refraction Relationships

 

 

Enrichment

NOVA (PBS) explains how refraction makes diamonds sparkle

 

 

 

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