Question

Give the condition for a lens to be a thin lens.

Answer 1

In optics, a thin lens is a lens with a thickness (distance along the optical axis between the two surfaces of the lens) that is negligible compared to the radii of curvature of the lens surfaces.

There are two basic kinds of lenses: converging, and diverging. A converging lens brings all incident light-rays parallel to its optic axis together at a point , behind the lens, called the focal point, or focus, of the lens.