• Question: What is the Doppler Effect?

    Asked by bobsta1998 to Ben, Jony, Mark on 24 Nov 2011.
    • Photo: Mark Basham

      Mark Basham answered on 24 Nov 2011:

      hi bobsta1998,

      The doppler effect is what happens when a source of waves is moving towards or away from you. A good example of this is when an emergency vehicle drives past you with its siren on it changes pitch/wavelength as it passes you.

      Here is a nice picture showing the effect,

      on the left the waves are shorter, and on the left longer because of the movement of the object.

      This also effects light, and this is how we know if other galaxy’s are moving towards or away from us, cause the light is shifted to the blue(shorter) or red(longer) end of the spectrum

    • Photo: Jony Hudson

      Jony Hudson answered on 24 Nov 2011:

      I can’t do better than Mark at explaining it.

      Here’s an interesting thing though. The Doppler effect is how radar guns that the police use to measure the speed of cars work. They send out some radio waves, and when it bounces off the car it changes because of the Doppler effect. The radar gun measures the incoming radio waves and works out the speed of the car. Clever, eh?!

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