What is the Doppler effect?

2000/04/26 Elhuyar Zientzia

• Fisika

The Doppler effect was described by Christian Johan Doppler in 1842 and therefore bears his name.

Suppose a source emits fixed and constant frequency waves. A fixed observer will observe that: the constant frequency wave. But when the source begins to move, the frequency of the wave emitted by the fixed observer will not be constant, but variable.

This is the Doppler effect: when the wave source and the observer are in relative motion, the frequency of the wave the observer receives as it approaches and moves away is less or greater.

Therefore, when you move away, the sound of the ambulance siren seems to us lower and when it approaches higher. But the sound is always the same.

The Doppler effect is applicable to sound, light or radio waves. This effect allows to measure the relative movement of a star or galaxy with respect to the earth.