What is the Doppler effect?

The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the source of the wave. This phenomenon is commonly observed with sound waves but also applies to electromagnetic waves such as light.

Explanation

• When the source of the wave moves towards the observer, the waves are compressed, leading to a higher frequency and a shorter wavelength. This is why a siren sounds higher-pitched as it approaches you.
• When the source moves away from the observer, the waves are stretched, resulting in a lower frequency and a longer wavelength. This causes the siren to sound lower-pitched as it moves away.

Applications

• Sound
  • Ambulances or police sirens sound higher-pitched as they approach and lower-pitched as they move away due to the Doppler effect.
• Light:
  • In astronomy, the Doppler effect is used to determine the movement of stars and galaxies. When a star moves away from Earth, its light shifts towards the red end of the spectrum (redshift). When it moves towards Earth, the light shifts towards the blue end (blueshift).
• Radar and Sonar:
  • Used in radar guns to measure the speed of vehicles and in sonar systems to detect objects underwater.
• Medical Imaging:
  • Doppler ultrasound is used to measure blood flow in vessels.

The Doppler effect provides crucial information in various fields, including astronomy, medicine, and navigation