Investigations with ray streaks
In these experiments, students look at the behaviour of rays of light. These 'rays' are not ideal rays, but narrow streaks or blades of light that emerge from the slits of a comb illuminated by a small lamp. They see for themselves some important properties of lenses, rays and images - effectively drawing ray diagrams in light. As well as showing the action of lenses and mirrors, the experiments model a variety of optical instruments. Some of these experiments could be set up as a circus with groups of students moving from one to the other.
If laboratory benches are not long enough, or flat enough, board can be placed on a bench (or two stools), painted white or covered in white paper to show up the ray streaks.