A concave lens is thinner in the middle and thicker at the edges, and is also known as Diverging Lens.

A convex lens is thicker in the middle and thinner at the edges, and is also known as Converging Lens.

Quantity: 1 x 50mm diameter glass Concave lens and 1 x 50mm diameter glass Convex lens.

Material: Optic Glass.

Focal Length: 20cm

Concave is used in glasses, some telescopes, spy holes in the doors, etc. It is also used for the correction of the problem in short sight

Convex is used in the camera, focus sunlight, overhead projector, projector microscope, simple telescope, magnifying glasses, etc. It is also used for the correction of the problem in long sight.