Optics experiments and demonstrations

Optics is the study of light and how it behaves, and many of its principles can be shown through straightforward experiments. Light usually travels in straight lines, which is why objects cast sharp shadows and why a pinhole can form an image. When light meets a surface it can be reflected, transmitted or absorbed, and demonstrations with mirrors show the law of reflection: a ray bounces off a smooth surface at the same angle at which it arrives.

Refraction, the bending of light as it passes from one transparent material into another, is another core topic. A pencil appearing to break at the surface of a glass of water is a familiar example, and passing a beam through a glass block lets the bending be measured. Lenses use refraction to converge or spread light, forming the images produced by magnifying glasses, cameras, telescopes and the human eye. Experiments with converging and diverging lenses show how image size and position depend on the object's distance.

Colour and the spectrum give some of the most striking demonstrations. A glass prism splits white light into a band of colours because each wavelength is bent by a slightly different amount, the same effect that produces a rainbow when sunlight passes through raindrops. Other experiments explore how coloured filters and pigments work, how colours combine, and how the eye perceives them. Together these demonstrations connect everyday observations — shadows, reflections, rainbows and lenses — to the physics of light, and they link to wider topics such as waves and the nature of the electromagnetic spectrum.

Frequently asked questions

Why does a straw look bent in a glass of water?

Light bends, or refracts, as it passes between water and air, so the part of the straw seen through the water appears shifted from the part above it.

How does a prism create colours?

A prism bends each wavelength of light by a slightly different amount, spreading white light into the band of colours that make up its spectrum.

What is the law of reflection?

When light reflects from a smooth surface, the angle at which it leaves equals the angle at which it arrived, measured from a line perpendicular to the surface.