What is meant by refraction?

53 What is the consequence of making angle of incidence of light, at an interface, greater than the critical angle? 54 With the help of a labeled ray diagram show the formation of image of an object by a compound microscope. 56 Express the refractive index of the medium. 57 If a ray of light passes from medium I to medium II without any change of direction, what can be said about the refractive indices of these media.