Explain in detail the image formation by a pinhole camera.

The formation of an image by a pinhole camera can be understood by a simple ray diagram shown below.

Consider an object XY kept in front of the pinhole O of the camera. Although light rays from the object travel in all directions, we will only take those rays into consideration that pass through the pinhole and thus contribute to image formation.

A ray of light coming from point X travels along XO, passes through the pinhole O and finally falls on the screen at X'. Similarly, a light ray coming from point Y travels along YO, passes through the pinhole O and falls on the screen at Y'. All the other rays which start between X and Y pass through the pinhole and fall on the screen between X'and Y'. While passing through the pinhole, the light rays intersect and cross over. Thus, the final image Y'X' is an inverted image of the object XY.