Condition for Zero Doppler Effect in Classical Theory, Special Relativity and New Approach 


The Doppler effect (DE) has a wide application in many areas of science and technology. Radiofrequency technologies that use this effect are based on the classical DE theory. We know that since 1905, we have the relativistic theory of DE. Recently, a new DE theory based on relative velocity between wavefronts and wave source/observer has been proposed. In this paper, we will examine the condition for the vanishing of DE, that is, no frequency shift irrespective of the relative motion between the wave and the wave source/observer. Examination will be done to the three theories of DE.