In Figure, light is initially in a medium (such as air) of index of refraction n 1 . It is incident at angle 1

In Figure, light is initially in a medium (such as air) of index of refraction n₁. It is incident at angle θ₁ on the surface of a liquid (such as water) of index of refraction n₂. The light passes through the layer of water and enters glass of index of refraction n₃. If θ₃ is the angle of refraction in the glass, show that n₁ sin θ₁ = n₃ sin θ₃. That is, show that the second medium can be neglected when finding the angle of refraction in the third medium.

n2 (n2 > n) n3 (n3 > n)