physics · 3d
DOPPLER EFFECT
Watch wave fronts compress and stretch as a source moves. From blueshift to sonic booms — all in real time.
Source at rest. Wave fronts form perfect concentric circles. Observed = source frequency.
Source freq440 Hz
Observed440 Hz
Shift—
Mach №0.00
Waves0
1× speed
Source
Observer
Blueshift (higher f)
Redshift (lower f)
No shift
A — Theoretical - - - source reference | ━━ observed (Doppler formula, instant)
B — Measured from wave arrivals ━━ observed | │ tick = ring hits observer (has travel-time lag; shows real transitions)
The Doppler Formula
fobs = fsrc × vsound / (vsound − vsrc · cos θ)
θ = angle between source velocity and direction toward observer.
When source approaches (θ≈0°): denominator shrinks → blueshift (higher pitch).
When source recedes (θ≈180°): denominator grows → redshift (lower pitch).
At Mach 1 the denominator → 0, fobs → ∞ — wave fronts pile up at source.
Beyond Mach 1 a Mach cone forms with half-angle α = arcsin(1/M).
The ring color encodes the Doppler shift each segment of a wave front would carry: blue half faces the direction of motion (compressed), red half trails behind (stretched).
The oscilloscope draws the waveform using the instantaneous Doppler formula evaluated at each frame — it's a theoretical prediction, not measured from individual wave-ring arrivals. For a more accurate capture you'd track each ring reaching the observer and measure inter-arrival periods; the formula gives the same steady-state result once the source is moving at constant velocity.
When source approaches (θ≈0°): denominator shrinks → blueshift (higher pitch).
When source recedes (θ≈180°): denominator grows → redshift (lower pitch).
At Mach 1 the denominator → 0, fobs → ∞ — wave fronts pile up at source.
Beyond Mach 1 a Mach cone forms with half-angle α = arcsin(1/M).
The ring color encodes the Doppler shift each segment of a wave front would carry: blue half faces the direction of motion (compressed), red half trails behind (stretched).
The oscilloscope draws the waveform using the instantaneous Doppler formula evaluated at each frame — it's a theoretical prediction, not measured from individual wave-ring arrivals. For a more accurate capture you'd track each ring reaching the observer and measure inter-arrival periods; the formula gives the same steady-state result once the source is moving at constant velocity.