Refraction- semi circular slab

Question

1)why does no refraction occur as teh ray passes through the semi cirular face while it does bend passing through the flat surface?

2) what happens when a light ray:

*passes from one medium (air) to another medium (acrylic plastic) at an angle of 90*?

*passes as before but at an angle not 90*? (i does not = 0*)

* passes from teh acrylic plastic back into the air?

thanks

Answer 1

1) When light ray is incident at 90 deg the ray passes through the medium without any refraction. If the incident ray hits the center of a semi-circular face, the incident angle is 90 deg at all points, so there is no refraction.

2a) No refraction

2b) the ray will converge. (move towards the vertical)

2c) the ray will diverge.Divergent angle will be greater than incident angle.

Remember the formula: refractive index = sine(incident angle)/sine (divergent angle)

-TJ