Classroom Experiments Testing Constancy of Speed of Photons

Special Relativity (SR) is the cornerstone for modern physics and variety of applications. SR is based on two postulates, the principle of relativity (the first postulate) and the principle of constancy of speed of light (the second postulate). Recently we have (1) shown that the light propagate as particles/photons in the “pure” wave experiments, such as double slit and grating experiments; (2) proposed experiments to measure the speed of the photons by an observer moving relative to the source and thus, to test the second postulate for photons. In this article we propose a classroom experiment to test the second postulate. If the experiments show the existence of interference pattern (the negative result), the constancy of the speed of the photons holds, namely the second postulate of SR is experimentally confirmed. If the experiments show no interference pattern (positive result), then the propagation speed of photons is not constant, namely, the second postulate of SR is disproved. Either negative result or positive results would be profoundly significant.