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Question

A narrow ray of yellow light from glowing sodium (λ0 = 589 nm) traveling in air strikes a smooth surface of water at an angle of θi = 40.5°. Determine the angle of refraction θr.

Answer 1

Use Snell's law.

 

n₁sinθ₁ = n₂sinθ₂

 

n₁ = index of refraction of air (look it up, it is close to 1.00)

n₂ = index of refraction of water (look it up, it is > 1))

θ₁ = θ_i = 40.5º

θ₂ = θ_r = ?

 

n₁sin40.5° = n₂sinθ_r

 

θ_r = arcsin[(n₁/n₂)sin40.5°]

 

Look up n₁ and n₂, and then just plug in the numbers.