Pinhole camera

Explanation

Construction of a pinhole camera:
Pinhole camera : This is a device which forms a photograph-like image of a stationary bright object on a screen . This works on the rectilinear propagation of light.
A pinhole camera consists of a cubical or cylindrical empty cardboard box with a fine hole on one side and with a paper or glass on the opposite side that any light which falls on its walls directly or indirectly is absorbed . When a stationary bright object (AB) is placed in front of a pinhole camera, an inverted impression `(A^(1)B^(1))` can be seen on the screen . To take an actual photograph, the pinhole camera is covered with a thick black cloth an the screen is replaced by a photographic film . The camera is faced towards the objects to be photographed and the black cloth is removed only from the side of the pinhole . The film gets exposed to the light coming from the object through the pin hole. The film is developed and printed in studio. The size of the image formed by a pinhole camera depends on the distance of the screen or film behind the pinhole . To compare the size of the image with the size of the object, we define the term magnification.

Magnification (m)` =("Size of image (i)")/("size of object (o)")`
`=("Distance of image (v)")/("Distance of object (u)")`
`=("Width of the pinhole camera")/("Object distance")`
Note : Normally we use 'u' ot represent object distance and 'v' to represent image distance and both are measured from the optical instrument.