Image Formation by Lens

Lens

A piece of transparent material

Two types of lenses

Convex lens and concave lens

Parallel light rays passes through convex lens

Converge at a focal point, F

Parallel light rays passes through concave lens

Diverging from a focal point, F

Focal point of convex lens

Real

Focal point of concave lens

Virtual

Focal length, f of convex lens

Positive

Focal length, f of concave lens

Negative

Optical centre, O

Point at the centre of the lens

Light rays passing through optical centre

Not refracted