.The pinhole camera

In the pinhole camera, the lens is replaced by a pinhole, and the focal diagram degenerates to the diagram at left. Explore the similar triangles. What controls the relative size of the image?

You can make your own pinhole camera. You will need a (Kodak) 126 film cartridge. Make a cardboard box with no back to fit the cartridge. The inside of the box should be painted black, and all edges and connections taped so no light can enter. Make a tiny pinhole in aluminium foil at the front and provide a black light-proof cover.

When all is ready, wind the film on, and fix your camera firmly in position to take your photo. You will have to experiment, but using ASA 200 film, you may find that one to three seconds gives a good exposure. Wind the film on for the next shot. You should find that you can take quite reasonable photos.