GENERAL KNOWLEDGE

Detailed explanation-1: -The waves travel at the same speed, but the observed frequency depends on any relative motion between the observer and source. When the observed frequency changes, so does the wavelength. If the observer and source are moving toward each other, then the frequency increases and the wavelength decreases.

Detailed explanation-2: -When the source and observer are moving relative to each other, the frequency observed by the observer (fa) is different from the actual frequency produced by the source (f0). This is basically the definition of the Doppler effect in Physics.

Detailed explanation-3: -The Doppler effect describes the change in the observed frequency of a wave when there is relative motion between the wave source and the observer. It was first proposed in 1842 by Austrian mathematician and physicist Christian Johann Doppler.

Detailed explanation-4: -if the source is moving away (positive velocity) the observed frequency is lower and the observed wavelength is greater (redshifted). if the source is moving towards (negative velocity) the observed frequency is higher and the wavelength is shorter (blueshifted).