Equations
Doppler effect (source approaching a still observer)
Waves · id doppler_approaching
f = f_s \frac{v}{v - v_s}
| Symbol | Quantity | Unit | Meaning | Usual range |
|---|---|---|---|---|
f | observed frequency | Hz | Frequency the observer hears | 0 to 1e+06 |
fs | source frequency | Hz | Frequency the source emits | 0 to 1e+06 |
v | speed of sound | m/s | Speed of sound in the medium | 100 to 2000 |
vs | source speed | m/s | Speed of the source toward the observer | 0 to 300 |
Assumptions
- Observer at rest
- Source moves straight toward the observer
- Still air
Valid when
- Source slower than sound
Found by
Questions with these words retrieve this equation: doppler, siren, ambulance, pitch, approaching, train horn, frequency shift.
Source
OpenStax University Physics Volume 1, Chapter 17 (reference; entry written by the project). License: MIT. Entry confidence: 0.97.