Science · 6 pages · 12 min
How Doppler shift changes a siren
The siren sounds higher while approaching and lower while leaving, because the waves bunch and then stretch.
When the purchase is complete, return to the original window. It will refresh.
From the opening
Doppler shift changes a siren because motion changes the spacing of the waves that reach you. An approaching source crowds the wavelength, so the pitch rises, and a receding source stretches it, so the pitch falls. The opening covers shorter wavelength ahead of the source, why listener motion is not identical, and the drop at the moment of passing.
The rest of the brief — the later sections and the reading notes — opens after Stripe confirms payment.
Inside
- Shorter wavelength ahead of the source
- Why listener motion is not identical
- The drop at the moment of passing
- The same idea in radar and light
- Where the idea stops applying
- A distinction worth keeping
Sources
- The Doppler effect for a moving sound source
- Wavelength compression along the line of motion