# Light cone from water-air

by daveed
Tags: cone, light, waterair
 Mentor P: 41,456 Consider the light emitted at all angles. What's the angle of the refracted light if the angle of incident light is $\theta$? As the angle of incidence gets larger, at some angle (the critical angle) you won't get any refracted light. You'll have so-called "total internal reflection". Figure out that angle, then use it to figure out the diameter of the "cone" of light that emerges from the water.