Nicol prism

The Nicol prism is made from a naturally-occurring mineral named Iceland spar. Its crystals have a special double refracting quality, which William Nicol exploited in his invention of 1829, when he cut a rhomb in half, reversed one half, and glued them together with Canada balsam, to form a rhomb similar in appearance to the one he had to start with. This can now split the light into polarised and unpolarized rays.

The Nicol prism is a device which polarises light by exploiting the ability of Iceland spar to split incident light into two beams with different characteristics: one beam is extracted at an internal surface and by choosing an appropriate geometry, the emerging beam can be fully polarised. Used in pairs, as polarise and analyser, the Nicol prism enabled minerals to be identified from optical characteristics which derive from their mineral structures.

The Nicol prism was also used in polarimeters, devices which were used to measure the sugar content of solutions, or in a medical context to calculate whether a patient was diabetic. By rotating one prism relative to the other, it was found that the brightness of the reflected beam could be varied and even extinguished.

Record details

To search on related items, click any linked text below.