Question

Suppose that light entered one side of a square water droplet of refractive index 1.33 at an incident angle of 14 ∘∘. Some of the light reflects off the back surface and then goes back out on the same side as it entered. Find the angle of refraction of light leaving the square droplet.

Answer 1

see the ray diagram :

The ray enters at an angle i = 14 degree, then it goes inside say at an angle r (angle of refraction). Now this ray hits the back surface, where total internal rflection occurs. From symmetry we can say the angle of incidence at back surface is equal to r, then angle of reflection is also r and after this, angle of incidence on the surface from which it entered is r.

Now, when it refract to the outside medium, the angle of refrction is r'.

Applying Snell's Law at entry :

[n = refractive in dex of water]

Applying Snell's Law at exit :

Comparing the two equations, we get r' = i = 14 degree. [answer]