Description
A prism consists of a translucent piece of glass or crystal, usually triangular in cross section, which is used to separate light into a spectrum of its separate colours.

The instrument works because different wavelengths of light are refracted (bent) by different amounts as they enter and leave the prism; the shorter wavelengths (towards the blue end of the spectrum) are refracted by the greatest amount, and the longer wavelengths (towards the red end) are refracted the least. This spreads out normal white light, which is a mixture of all the different colours, into its constituent parts and produces the rainbow effect of a spectrum.

This prism belongs to the Cavendish Laboratory, Cambridge, and was reputedly owned by Isaac Newton, though this is certainly fanciful. Analysis by the researcher A.A. Mills into the physical and optical properties of this prism (and the similar Wh.1254) lead him to conclude that "These flint glass prisms, which are a little more dispersive than the British Museum prism, again do not match any of Newton's recorded prisms. ... None of the extant prisms claiming an association with Newton can be identified with any of his recorded prisms."
18/10/2002
Created by: Saffron Clackson on 18/10/2002