Physics - question

Question

Find the angle of incidence in the water that gives the boundary angle for total reflection in it

later the transition between glass and air.

Which option is right?

Answer 1

From the wording of the question, it looks like you want to analyze for total internal reflection going from medium 1 to medium 2. Use Snell's law.

n₁sinθ₁ = n₂sinθ₂

n₁ = index of refraction of medium 1 (look it up)

n₂ = index of refraction of medium 2 (look it up)

θ₁ = angle of incidence crossing from medium 1 to medium 2 = ? (what you are trying to find)

θ₂ = 90° (total internal reflection)

sinθ₁ = n₂sinθ₂ / n₁ = (n₂/n₁) sin90° = n₂/n₁

θ₁ = arcsin(n₂/n₁)

Note that n₂ ≤ n₁ to give total internal reflection.