What name is given to the ratio of sine of angle of incidence to the sine of angle of refraction?

How must light travel out of a substance if it is not going to be refracted?

Draw and complete the following diagrams to show what happens to the beams of light as they enter the glass block and then leave it:

Write the relation between the angle of incidence and the angle of refraction for a medium.

What is the unit of refractive index?