Concave Lens and Use of Convex Lenses - The Camera

A lens having both of its surfaces curved inwards is called as a concave lens. It is thin in the middle and thicker at the edges. It is also called as a diverging lens as it diverges a parallel beam of light rays incident on it.

Convex lenses are thicker at the middle. Rays of light that pass through the lens are brought closer together (they converge). A convex lens is a converging lens.

When parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.

The distance between the principal focus and the centre of the lens is called the focal length.

Use of Convex Lenses – The Camera

A camera consists of three main parts.

1. The body which is light tight and contains all the mechanical parts.
2. The lens which is a convex (converging) lens).
3. The film or a charged couple device in the case of a digital camera.