Question

write the rules of refraction for a spherical lense

Answer 1

Rule 1

       When a ray of light goes from an optically rarer medium to an optically denser medium, it bends towards the normal. In this case the angle of refraction will be smaller than the angle of incidence. For example, when a beam of light goes from air into water, it bends towards the normal. In the similar manner when a beam of light goes from air into glass or from water into glass, it bends towards the normal. 



Rule 2

        When a ray of light goes from an optically denser medium to an optically rarer medium, it bends away from the normal. In this case the angle of refraction will be greater than the angle of incidence. For example, when a beam of light goes from water into air, it bends away from the normal. In the same way when a beam of light goes from glass into air or from glass into water, it bends away from the normal.