Doppler Shift in Sound
When a man is standing at the railway crossing, the frequency of the whistle emitted by the train while it is approaching and crossing changes. The reason behind this phenomenon is the Doppler shift. As the source moves toward the observer, the frequency of the sound wave will appear to increase, and as the source moves away from the observer, the frequency will appear to decrease. So, that is the reason behind the difference in the pitch of the sound of the whistle emitted by the train as it is approaching and moving away. If the source is moving toward the observer, then the velocity of the source is positive, and it is negative as it moves away from the observer. If the observer is moving toward the source, then the velocity of the observer is positive, and it is negative as it moves away from the source.
Difference between Doppler Effect and Doppler Shift
Doppler effect or Doppler shift phenomenon was described in 1842 by an Austrian physicist, Christian Doppler, and it is named after him. The Doppler effect or Doppler shift is a change (increase or decrease) in the frequency of a wave as the source and the observer move (towards or away from) each other relative to the medium. Based on the direction of the source and the observer and the magnitudes of their velocities, the observed frequency can be less or more than the source frequency. For example, the pitch of the sound of an ambulance siren changes as it passes us. It happens because of the relative velocity between the source and the observer. When the ambulance is approaching us, the relative velocity is negative, and the relative velocity is positive when it is moving away. So, that is the reason behind the difference in the pitch of the sound of the ambulance siren while it is approaching and while it is moving away. The Doppler effect applies to all types of waves, including sound and light. The Doppler effect is responsible for the Blue Shift or Red Shift phenomenon observed in light waves. The Doppler effect is used in various fields such as radar, astronomy, satellite communication and navigation, medical imaging, etc.
Contact Us