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Physics vocabulary · Waves, Oscillations and Sound

Doppler effect

Meaning in physics, with examples

nounCommon term

In physics, Doppler effect means: The change in the observed frequency of a wave when the source and the observer move towards or away from each other. A siren sounds higher as it approaches and lower as it moves away.

In Turkish: Doppler olayı, Doppler etkisi

How it is used

Applies to both sound and light. In astronomy, light from galaxies moving away from us is redshifted, which is evidence that the universe is expanding. Police speed guns, medical ultrasound and weather radar all use the Doppler effect. Also called the Doppler shift.

Example sentences

  1. The Doppler effect explains why the ambulance siren drops in pitch as it passes us.

  2. Astronomers use the Doppler effect to measure how fast stars are moving towards or away from us.

Common collocations

  • Doppler shift
  • redshift
  • blueshift
  • Doppler radar
  • Doppler ultrasound
  • frequencyThe number of complete waves or oscillations that pass a point, or happen, each second. It is measured in hertz (Hz), where 1 Hz means one cycle per second.
  • wavelengthThe distance between two neighbouring points on a wave that are at the same stage of their cycle, such as two crests. It is shown by the Greek letter lambda (λ).
  • waveA disturbance that travels through a medium or through space and carries energy from one place to another without carrying matter with it.
  • electromagnetic spectrumThe full range of electromagnetic waves, ordered by wavelength or frequency: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.

More terms: Waves, Oscillations and Sound

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