Investigating the Doppler Effect when the Wave Source Moves in a Circular Path

Abstract

The commonly known Doppler Effect formula is used to calculate the observed frequency for an observer and a source that move relative to each other with constant velocity. However, this formula has a constraint: the relative movement between the source and the observer must be linear because if not, then due to change in direction, relative motion is not in constant velocity anymore. Additionally, when the source and observer move in relative linear motion, there is no change in the direction in which they approach or move away from each other and hence the wavelength of the observed wave is constant (and so is the observed frequency). However, when a wave source moves in circular motion, due to continuously changing velocity, there is a continuous change in the direction and hence the wavelength (and frequency) of the observed wave is always changing. Hence, to help observe this effect of Doppler Effect in circular motion better, this investigation was designed to focus on knowing how the change in the speed of the wave source when moving in a circular path affects the observed frequency.