Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

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.


Experiments with a fan of rays

Experiments with a single ray

Model of a camera

Depth of field for a camera

Model of a telescope with ray streaks

Ray model of telescope with field lens

Model of a microscope with ray streaks

Model of a microscope using a car lamp

Related Guidance

About telescope lenses

Ray streaks and ray diagrams: some cautions

Ray box or lamp?

Teaching ray optics