The Doppler Effect and Shock Waves · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Why the siren changes pitch as it passes

Science · Waves, Light & Sound · ages 18-20
Name ______________________   Date ____________

  1. Moving source versus moving observer: what differs physically?

    • Only the loudness changes
    • Wavelength rewrite versus meeting rate change
    • Only the wind matters

  2. Why is the approaching siren higher pitched?

    • Crests bunch ahead of the moving source
    • Air conducts treble better
    • The siren plays new notes

  3. A supersonic jet booms exactly once when it breaks the barrier.

    Circle one:   True   False

  4. A stationary listener hears a receding siren. What arrives?

    • A lower pitch than emitted
    • A higher pitch than emitted
    • Silence until it stops

  5. When do the two formulas disagree enough to care?

    • At walking pace
    • Only where there is no air
    • Near the wave speed

  6. A jet flies at twice the wave speed. What is sine of the cone half angle?

    Answer: ______________

  7. Near the wave speed, a student swaps in the wrong case formula. What is the error?

    • All Doppler formulas always match
    • Speed differences never matter
    • Source and observer formulas differ there and cannot swap

  8. What is a shock wave and when does it form?

    • A single bang at takeoff
    • Piled crests coning behind a supersonic source
    • Faster radio signals
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Why the siren changes pitch as it passes W1-mt_UVfD_coqh6-s1

  1. Wavelength rewrite versus meeting rate change · One rewrites the wave in the medium, the other only meets it faster.
  2. Crests bunch ahead of the moving source · Bunched crests shorten the wavelength the listener meets.
  3. False · The cone trails the jet, booming each listener as it passes.
  4. A lower pitch than emitted · Stretching behind the source lengthens the met wavelength.
  5. Near the wave speed · Slow motion makes both formulas nearly identical.
  6. 0.5 · Sine of theta is wave speed over source speed: one over two.
  7. Source and observer formulas differ there and cannot swap · The two mechanisms split apart exactly where speeds run high.
  8. Piled crests coning behind a supersonic source · Outrunning the waves stacks every crest onto one cone.
Worksheet · LightMySky