Refraction problems and total internal reflection
Answers are for parents and teachers.
1
The angle between incident and reflected rays is 60°. What is the angle of incidence in degrees?
30
2
How far does light travel in water (n = 1.33) in 4·10⁻⁹ s? (c = 3·10⁸ m/s)
v = c/n ≈ 2.26·10⁸ m/s; s = vt ≈ 0.9 m
3
For a substance–air boundary with refractive index 1.25, what is the sine of the limiting angle?
sin α₀ = 1/1.25 = 0.8 (α₀ ≈ 53°)
4
A ray goes from under water toward the air at 60°. Does it leave the water? (α₀ ≈ 49°)
No, 60° > 49°, so the ray is totally reflected.
5
Name two uses of fibre-optic cables.
For example, internet communication and the medical endoscope.