Where does prism collide?

In optics, a prism is a transparent block, usually a triangular wedge, that refracts light at its sloping faces and, because the refractive index varies with wavelength, spreads white light into its component colours. Newton's 1672 letter to the Royal Society, A new theory about light and colours, used a prism to show that white light is a mixture of rays of differing refrangibility rather than a pure substance the glass stained. The referent is a dispersing or deviating optical element, characterised by its apex angle and material dispersion, and it is a different thing from the hollow solid of the same name in geometry, which does nothing to light.[1]

Unit

The angular dispersion and deviation a wedge imposes on light

Recovery means

Not applicable

Measured by

Characterised by the angle of minimum deviation, the apex angle, and the material's dispersion across wavelengths

In solid geometry, a prism is a polyhedron with two congruent, parallel polygonal faces, the bases, joined by parallelogram faces, so that any cross-section parallel to the bases is identical. Euclid's Elements defines the prism and derives the volumes of such solids, fixing a purely spatial object whose properties are its base shape, height, and the resulting volume and surface area. The referent is an abstract shape studied for its measure and symmetry, and it bears no relation to the behaviour of light; a glass optical prism is merely one physical object that happens to take this form.[2]

Unit

The volume and surface area of the solid, from base and height

Recovery means

Not applicable

Measured by

Computed from the base area and height for volume, and from face areas for surface area