Prism
A 3-dimensional solid object with two identical ends and flat sides. The shape of the ends gives the prism its name, such as the triangular prism shown below. When a beam of white light (for example from the Sun) interacts with a glass or plastic prism, it is dispersed into a spectrum. We see the coloured spectrum when it reflects off a surface.
A beam of white light from a source on the right passes through a thin slit and triangular prism. The prism disperses the white light into its component wavelengths and a spectrum is produced. We see the coloured spectrum as it reflects off the wall. Image source: Pearson Education Inc.
