When the wave source is leavingД¬onversely, when the source of waves is moving away from the observer, each crest of the wave is emitted from a position farther from the observer than the previous wave.

The time between the arrivals of successive wave crests at the observer is reduced, increasing the frequency. Therefore, each wave takes slightly less time to reach the observer than the previous wave. When the source of waves is moving towards the observer, each successive wave crest is emitted from a position closer to the observer than the crest of the previous wave. Using the Doppler effect, we can calculate how fast the ambulance is moving based on the change in sirenвЂ™s frequency. For example, when an ambulance is approaching us, the sirenвЂ™s pitch will increase, and when it is travelling away from us, the pitch will lower. Doppler effect is the change in frequency of a wave in relation to an observer who is moving relative to the wave source.ДЄccording to the Doppler effect, waves like sound waves will change in pitch when there is a change in frequency. What is the Doppler effect?ДЄround 40 years before the Second World War in 1842, Austrian physicist Christian Doppler described a phenomenon what is now called the Doppler effect or Doppler shift. Since then Doppler radar technology has come a long way and is now used by national weather services, research institutions and weather departments of television stations. Scientists began to study this phenomenon. Basically, Doppler radar uses radio waves to observe precipitation and wind in the area around the radar station.Дuring the Second World War, radar operators discovered that weather was causing echoes on their screen, masking potential enemy targets. The term вЂradarвЂ™ is an acronym for вЂradio detection and rangingвЂ™. Doppler weather radar detects precipitation, such as rain, snow, hail, and other weather phenomena.

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