Refraction

• The phenomenon, due to which a ray of light deviates from its original path, while traveling from one optical medium to another optical medium is called refraction.
• When a ray of light travels from optically rarer medium to optically denser medium, it always bends towards normal, drawn at the point of incidence.
• When a ray of light travels from optically denser medium-glass or water- to optically rarer medium – air or vaccum, it always bends away from the normal, drawn at the point of incidence.
• When an incident ray strikes at right angles at the point of incidence, it suffers no refraction.
• The perpendicular shift in the path of incident ray, while emerging out from an optical slab is called lateral displacement.
• The lateral displacement is

(i) directly proportional to thickness of optical slab

(ii) directly proportional to refractive index

(iii) directly proportional to angle of incidence

(iV) inversely proportional to wave-length of light

• Because of refraction

(i) a stick appears bent and short when immersed obliquely in water. It also appears magnified because image is formed close to the eye.

(ii) the bottom of a beaker filled with water appears raised. Swimming pool appears shallow when filled with water.