Doppler Effect, Definition of Doppler Effect, Details of Doppler Effect (For CBSE, ICSE, IAS, NET, NRA 2022)

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Doppler Effect

When an ambulance crosses you with its siren blaring, you hear the pitch of the siren change: as it approaches, the siren՚s pitch sounds higher than when it is moving away from you. This change is a common physical demonstration of the Doppler effect.

Example of Doppler Effect

Example of Doppler Effect

Definition of Doppler Effect

  • It is an important phenomenon that is useful in a variety of different scientific disciplines, including planetary science: Astronomers rely on the Doppler effect to detect planets outside of our solar system or exoplanets.
  • Doppler shift or effect describes the change in frequency of any kind of sound or light wave produced by a moving source with respect to an observer.
  • Waves emitted by a source travelling towards an observer get compressed.
  • In contrast, waves emitted by a source travelling away from an observer get stretched out.
  • “Doppler Effect is an increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move towards (or away from) each other”
  • Many mistaken that the Doppler effect to be applicable only for sound waves. But It should be noted that the Doppler effect doesn՚t just apply to sound. It works with all types of waves including light.
  • Edwin Hubble used the Doppler Effect for determining that the universe is expanding. Hubble found that the light from distant galaxies was shifted toward lower frequencies, to the red end of the spectrum.
  • This is known as a red Doppler shift or a red-shift. If the galaxies were moving toward Hubble, the light would have been blue-shifted.
  • Doppler radars also help meteorologists learn about possible tornadoes

Details of Doppler Effect

Details of Doppler Effect
  • Doppler was the son of a stonemason, who went on to become a celebrated academic and scientist.
  • After school he studied astronomy and mathematics in Salzburg and Vienna, and at the age of 38 went on to work at the Prague Polytechnic in Czechoslovakia.
  • After a year later, he found fame by discovering that the observed frequency of light and sound waves is affected by the relative motion of the source and the detector (in other words their positions in relation to one another) – and this became known as the Doppler Effect.
  • On 17 March 1853, at the age of only 49, Christian Doppler died from respiratory disease in Venice.

Doppler Effect Formula

In physics, where the speed of the receiver and the source relative to the medium are lower than the velocity of waves, the relationship between emitted frequency and observed frequency is given by:


  • c = the velocity of waves in the medium
  • = the velocity of the source relative to the medium
  • = the velocity of the receiver relative to the medium

The frequency decreases if either is moving away from the other.

Applications of Doppler Effect

Some Doppler effect applications are provided in the points mentioned below:

  • Sirens
  • Radar
  • Astronomy
  • Medical Imaging
  • Blood Flow Measurement
  • Satellite Communication
  • Vibration Measurement
  • Developmental Biology
  • Audio
  • Velocity Profile Measurement

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