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Doppler Effect

About this simulation

Doppler Effect is a top view of a source emitting wavefronts as it moves. Students set the source speed as a Mach number from 0 to 2.5 and the source frequency from 100 to 800 hertz, and can show the Mach cone. Readouts give the pitch heard ahead and behind, the Mach number and the cone half-angle. It explains why an ambulance siren drops in pitch as it passes and what happens when a source reaches the speed of sound.

What students can explore

  • Raise Source speed and compare the Heard ahead and Heard behind readouts.
  • Set the speed to Mach 1 and watch the wavefronts pile up in front.
  • Go above Mach 1 with Show Mach cone on and read the Cone half-angle.
  • Change Source frequency and see which readouts scale with it.
  • Set speed to 0 and check that both pitches equal the source frequency.

Learning objectives

  1. 1Explain why observed frequency changes when a source moves.
  2. 2Calculate heard frequency ahead and behind a moving source.
  3. 3Describe how a Mach cone forms at supersonic speed.
  4. 4Relate the cone angle to the Mach number.

Questions teachers ask

Is the Doppler Effect simulation free?

Yes. It is free, requires no sign-up and runs in any modern browser, including classroom whiteboards and tablets.

Why does a siren sound higher as it approaches?

The source moves toward you between emitting wavefronts, so they arrive closer together. Shorter spacing means a higher frequency, and the pitch drops once the source passes and the waves stretch.

How do I use it?

Set the Mach number and the frequency, then watch the rings. Read the pitch heard ahead and behind. Turn on the Mach cone to see the shock wave above Mach 1.

What is a Mach cone?

When a source moves faster than the waves it creates, the wavefronts overlap along a cone. Its half-angle satisfies sin theta equals the wave speed divided by the source speed.

Embed this simulation

Drop it into your LMS, blog, or class site — free.

<iframe src="https://kiwibee.io/en/simulations/doppler-effect-3d-simulation/embed" title="Doppler Effect | KiwiBee" loading="lazy" allowfullscreen style="width:100%;height:min(70vh,620px);min-height:420px;border:0;border-radius:16px"></iframe>

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