The objects bounded by one or two spherical surfaces, usually made up of glass is known as lens. There are two types of lenses:

I.  Convex Lens or Converging Lens

It is thick at the centre and thin at the edges. It converses the parallel rays of light on the focus.

II. Concave Lens or Diverging Lens

It is thin at the centre and thick at the edges. It diverges the parallel rays of light and appears to fall on the focus.

Nature of Image formed by Convex Lens

a) When object lies at infinity

– Image formed at focus.

– Image is real, inverted and highly diminished.

b) When object lies beyond 2F