Tales of Things

Nicol's Prisms

William Nicol of Edinburgh developed what is now called the Nicol prism in 1828. In the 17th century it had been discovered that Iceland Spar (a form of calcite) is double refracting, When a beam of light was shone perpendicularly on the surface of the crystal, one ray (the O or Ordinary ray) was transmitted without being refracted at the surface, while a second ray (the E or Extraordinary ray) was refracted and emerged parallel to the other ray. It was soon realised that the E and O rays were polarised at right angles to each other. Nicol used prisms made of calcite to produce polarised light for experiments. He altered the calcite crystals so that the E rays were totally reflected internally, leaving the O rays to emerge on their own from the crystal.

This unusually large set was made by C D Ahrens of London, specialists in the manufacture of prisms. It was probably made in the 1880s.

Created by: UoD_Museums on 17 Sep 2011, 5:53 p.m.

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