Refraction through Lens

Fig: Ray parallel to principal axis

Refraction of ray passing through the Principal focus:

A ray passing through principal focus emerges parallel to the principal axis after refraction from a convex lens.

Fig: Ray passing through focus

Fig: Ray passing through focus

A ray passing through the principal focus emerges parallel to the principal axis after diverging from a concave lens.

Ray passing through the optical centre of lens:

Ray passing through the optical centre of convex and concave lens emerges in same direction without any deviation.

Fig: Ray passing through O

Fig: Ray passing through O

Converging lens: A convex lens is known as converging lens because parallel rays converge at its focus.

Fig: Converging Lens

Diverging lens: A concave lens is known as diverging lens because parallel rays appear to diverge from the focus; after refraction.

Fig: Diverging Lens