Total reflection problems and the prism lab
Answers are for parents and teachers.
1
At the substance–air boundary sin α₀ = 0.75. Find the refractive index. Which substance does it match?
n = 1/0.75 ≈ 1.33 – water
2
In a medium n = 1.2. What is the speed of light in it, in m/s (c = 3·10⁸ m/s)?
v = c/n = 2.5·10⁸ m/s
3
In the prism lab α = 25° and γ = 14° (sin 25° ≈ 0.423; sin 39° ≈ 0.629). Find n.
n = 0.629/0.423 ≈ 1.49
4
Can total internal reflection happen when light goes from air to glass? Why?
No, because the ray goes from a rarer to a denser medium.
5
Why are right-angle prisms used in binoculars?
Total internal reflection is better than mirrors: no light is lost and the image is turned upright.