Fizeau Method

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Fizeau Method

 

a method of measuring the speed of light. The Fizeau method consists in selecting the rotation speeds of a toothed wheel so that a light beam is periodically interrupted by the teeth of the wheel, and the transmitted light pulse, after being reflected by a mirror located at a precisely measured distance, returns to the wheel and passes through one of the next gaps between the teeth. The speed of light is determined from the known distance between the wheel and mirror and the time required for the wheel to turn by an integral number of teeth (one, two, three, and so on). The Fizeau method was proposed and implemented by A.-H.-L. Fizeau in 1849. (See alsoSPEED OF LIGHT.)

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.