Question

show principal axis of concave and convex lens with the help of diagram​

Answer 1

A convex lens

• A convex lens also known as converging type because it converges a parallel beam of light rays passing through it. 

Principal axis :

• The principal axis of a lens is a line passing through the optical centre of the lens and perpendicular to both the faces of the lens. 

A concave lens

• A concave lens is known as diverging lens because it diverges the parallel rays of light passing through it. 

Principle axis

• The principal focus of a concave lens is a point on its principal axis from which light rays, originally parallel to the axis , appear to diverge after passing through the lens.