When rays travel from a denser medium to a less dense medium, we can define a critical angle of incidence θ꜀ such that the refracted angle θ₂ = 90°. Applying Snell's law:
Critical angle θ꜀ = sin⁻¹(n₂/n₁)

When the angle of incidence is greater than the critical angle, 100% of the light intensity is reflected. This is called total internal reflection because all the light is reflected. Calculate the critical angle for a glass and water combination. Show your calculation.