Speed of light measurement for the myriad

Abstract

We discuss a time-of-flight measurement of the speed of light which is inexpensive to build, has an experimental design completely accessible to students with a rudimentary knowledge of interference, and consistently produces values for c with errors of less than 1%. Students at the sophomore level can use the same apparatus to achieve uncertainties on the order of 0.25%.

A tabletop experiment for the direct measurement of the speed of light

“…To our knowledge, standard experimental textbooks do not contain expositions of an experiment such as ours. Many experiments to measure the speed of light have been presented, including a number of interesting time of flight measurements 1,2,3,4,5,6,7 . However, we could not find any that satisfied all the requirements.…”

An educational physics laboratory experiment for directly measuring the speed of light

“…The speed of light was estimated with a great mistake (25%) that was mainly due to the bad accuracy in the estimation of the Earth's orbit; even so, it became a well known fact -the speed of light is about several hundred thousand kilometers per second. Cooke et al (1968), and by Aoki et al (2008), although relatively imprecise in comparison with the interference methods (see James et al, 1999), enables direct measurement of the speed of light in the university/school physics laboratory. In the standard optical location methods the distance is determined by knowing the light velocity and measuring the time that it takes to the optical signal to travel along the distance.…”

Speed of light demonstration using Doppler beat

“…On the other hand, when using a modulated beam at a constant frequency, it is necessary to have a stabilised modulation. Phase shift measurements include amplitude-modulated light beams produced by means of Kerr cell [9], modulated LEDs [10,11], laser pointers [12,13], or modulated laser [14,15]. Recently, Pegna [16] has published an apparatus that modulates a collimated red laser at a frequency of 433.92 MHz, making possible a speed of light demonstration within a sub-metre measuring base.…”

“…The two different configurations described above are easily set up. It is possible to emulate the techniques described in [3,11], that is, an improved version of the rotating mirror technique and a variation of the interferometer of [9][10][11].…”