Question: What is the critical angle for total internal reflection?

Options:

1. sin(θc) = n2/n1
2. sin(θc) = n1/n2
3. θc = n1/n2
4. θc = n2/n1

Correct Answer: sin(θc) = n2/n1

Solution:

The critical angle θc can be calculated using sin(θc) = n2/n1, where n1 is the refractive index of the medium where the light is coming from.