• Question: what is the doppler effect?

    Asked by turbanator3000 to Jon, Katherine, Daphne, Cathal on 18 Mar 2012.
    • Photo: Daphne Ng

      Daphne Ng answered on 18 Mar 2012:

      The doppler effect is the change in frequency of a wave for an observer moving relative to the wave. The frequency is higher than the emitted frequency when the source of the wave is approaching the observer, identical to the actual frequency at the point of passing and lower when the source has moved away. The doppler effect is the reason why police sirens sound higher pitched (higher frequency) when they are far away and then decrease to low pitch (lower frequency) when the police car has passed you by.

    • Photo: Katherine Haxton

      Katherine Haxton answered on 18 Mar 2012:

      The doppler effect is really useful in astronomy as well, as light waves coming from a star or galaxy shift towards red or blue depending on whether objects are moving towards or away from us and is called red-shift or blue-shift.

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