Speed of Light Reflected From or Transmitted Through a Moving Medium: An Explanation of Fizeaus Experiment

Abstract

Musa D. Abdullahi

The speed of light reflected from or transmitted through a medium (glass or water) moving with speed v in another medium (air or vacuum), are derived in terms of the speed of light c in a vacuum and the refractive indices of the mediums. It is shown that the law of reflection of light applies irrespective of speed of the reflecting surface. A ray of light at normal incidence on a reflecting surface moving in the opposite direction of propagation of the ray, from a stationary source, is reflected with a speed greater than that of light c. The equation for speed of transmitted light in a moving medium, applicable for values of v from -c to c, is found to be different from that of Fresnel’s law obtained by relativistic considerations and applicable only if v << c. The non-relativistic equation, for the speed of light in a moving medium, is applied to explain the result of Fizeau’s experiment for the speed of light in moving water. It is concluded that the effect on the speed light in a moving medium is due to a media drag on the light ray, as envisaged by Fresnel, but not the result of relativistic addition of velocities.

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