Lenses (Physics)

Lens

A piece of specially shaped transparent material that can form focused image of objects

Convex (converging) lens

• A lens that is thicker at it centre.

• Converge parallel rays of light to produce a real image

Concave (diverging) lens

• A lens that is thinner at its centre.

• Diverge parallel rays to produce a virtual image

Optical Centre (O)

the point at the centre of the lens through which all rays pass without deviation.

Prinicipal Axis

the line that passes through its optical Centre and is perpendicular to the faces of the lens.

Principal Focus

the point on the principal axis through which all rays parallel and close to the axis converge, or from which they appear to diverge, after passing through the lens.

Focal length

(of a lens) the distance between its optical centre and it principal focus

Focal plane

the surface perpendicular to its principal axis and containing its principal focus.