Question

A meniscus lens has an edge thickness of 5mm and a diameter of 40mm. If the sag of the convex surface is 1.2mm and the sag of the other surface is 2.4mm, what is the centre of thickness of the lens?

Answer 1

Sag is given by the following equation:\[s( r )=\frac{ r ^{2} }{ 2R }\]where s( r) is the sag at radial position, r; and R is the radius of curvature of the surface.

Answer 2

Do you see how to solve the problem?