Trapped Light

Total internal reflection

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Going from a high n to a low n, light bends away from the normal.
• Beyond the critical angle, $\sin\theta_c = n_2/n_1$, all the light reflects.
• Total internal reflection makes diamonds sparkle and powers fibre optics.

Steps

1. Escaping glass
2. The critical angle
3. Find the critical angle
4. Diamonds
5. Trapped in water
6. Fibre optics