sir i want to know which lens is used in cameras and how it functions?

A camera is an instrument which gives a permanent image of the object.

A photographic camera consists of a convex lens fitted at one side of a light-proof box which is painted black from the inside.

A distance usually greater than twice the focal length of the lens should be maintained by the camera from the object to be photographed. The photographs of the distant and near objects are taken by adjusting the distance of the camera lens with the focusing ring. The view finder must focus the object properly before the camera is clicked. When the camera is clicked, light from the object falls on the camera, thereby forming a real, inverted and diminished image on the film.

After exposure, the film is treated with chemicals. The permanent image which is formed is called a negative. The negatives are used to get the positives which are called photographs.