Arturo O. answered • 11/24/17

Tutor

5.0
(66)
Experienced Physics Teacher for Physics Tutoring

Use Snell's law both at PQ and at PR.

Medium 1 is air, medium 2 is the glass.

At PQ:

n

n

θ

n

sinθ

sinθ

Medium 1 is air, medium 2 is the glass.

At PQ:

n

_{1}sinθ_{1}= n_{2}sinθ_{2}n

_{1}≅ 1θ

_{1}= α = 45°n

_{2}= √2sinθ

_{2}= (n1/n2)sinθ_{1}sinθ

_{2}= (1/√2)sin45° = 1/2θ

_{2}= 30°At PR:

ρ = angle between incident ray and normal to PR

n

_{2}sinρ = n_{1}sin90° [internal reflection at PR]√2 sinρ = 1

sinρ = 1/√2

ρ = 45º

Consider the triangle with corners at

(1) point P

(2) the point of incidence of the ray entering the glass at α = 45°

(3) the point where the ray inside the glass is reflected internally

(I know this is hard to see without a diagram, but I cannot upload a diagram.)

At (1), the angle is θ.

At (2), the angle is 90º + θ

_{2}= 90º + 30° = 120°At (3), the angle is 180° - (90° + ρ) = 180° - (90° + 45°) = 45°

Angles (1)+(2)+(3) = 180°

θ + 120° + 45° = 180°

θ = 15º

Hasan E.

11/25/17