4.2 Total Internal Reflection

4.2 Total Internal Reflection

Definition:

Total internal reflection occurs when light traveling from a denser medium to a less dense medium hits the boundary at an angle greater than the critical angle, causing the light to be completely reflected back into the denser medium instead of refracting. The critical angle θ_c can be found using:

sin θ_c = n₂ / n₁

where n₁ is the refractive index of the denser medium, and n₂ is the refractive index of the less dense medium.

Example Problem:

Calculate the critical angle for light passing from water (n = 1.33) into air (n = 1.00).

Solution:

Using the formula for the critical angle:
sin θ_c = 1.00 / 1.33 = 0.752
θ_c = arcsin(0.752) ≈ 48.6°
The critical angle is approximately 48.6 degrees.