Total Internal Reflection

AI Discussion of
What Makes a Diamond Sparkle.

Total Internal Reflection - PHET

showmethephysics Instruction

Assessment

Show Me The Physics

| Rutgers University Physics |

internalReflection2
 St. Mary's University

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Show Me The Physics

Show Me The Physics

2. Critical Angle θ_c– angle of incidence for which the angle of refraction equals 90⁰ when light travels inside one medium that borders on air or a vacuum

Deriving Critical Angle Equation

n₁sinθ₁ = n₂ sinθ₂

    Substitute θ_c, θ₂ = 90, n₂ = 1

n₁sinθc = 1sin90

n₁sinθ_c = 1

Ex) Find θ_c for Lucite

sin θc = 1/n₁

From reference table, n₁ = 1.50 

sinθ_c = 1/1.50

θ_c = 41.8

3. Total Internal Reflection

What is this called? 

Rutgers University Physics 

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(These kinds of fibers are coated with materials that have a low index of refraction (fast).
These materials are called cladding.)

St. Mary's University's Astronomy
 and Physics Dept.

When θ₁ > θ_c
Total Internal Reflection

(Outside Medium Must Be Faster)

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| Total Internal Reflection |

Rutgers U. Physics

Air

When θ₁ = θ_c

θ₂ = 90⁰

When θ < θ_c Refraction

Refraction of Light

Rick Reed

a) Total Internal Reflection?

Choice 2

(Outside Medium Must be Fast)

b) Refraction?

Choice 3

c) Impossible?

Choice 1

(Light always crosses over normal)

Dispersion

Enrichment

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St. Mary's U Astronomy and Physics Dept.