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D. Index of Refraction (n) – a comparison of the 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

    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) 

Ex 1) What is the speed of light in alcohol?    

n = 1.36 (Reference Table)

    n = 1.36 = c/v

1.36 = (3.00 x 10⁸ m/s)/V     

Mathematical relationship
between n & v?

n = c/v
 

1. Prediction θ_ref from θ_in

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

θ₂ = 32⁰  

b. n and V

n₁v₁ = n₂v₂

 

1 – incident medium
2 – refractive medium

 

When a light changes media, its wavelength changes NOT its frequency

c. n, λ

n₂λ₂ = n₁λ₁

Not in Reference Table

When light refracts it BENDS, CHANGES SPEED and WAVELENGTH 

Larger Version

Refraction and Wavelength- Don Ion

Total Internal Reflection