Answer
The light rays in a pinhole camera do not converge at a plane, so a pinhole camera can form an image with the viewing screen at any position.
Work Step by Step
The ray diagram for an image made by a converging lens is shown in Figure 28.47c. The light rays converge on a plane, so if the screen is moved away from that plane, the image will be fuzzy.
The ray diagram for an image made by a pinhole is shown in Figure 28.47b. The light rays do not cross over except at the pinhole, so no matter where the screen is placed, the image will be equally sharp.
The principle is discussed on pages 534-535.
