Wave Animation
Frequency Display
Waveform Comparison
Doppler Parameters
Source Parameters
Observer Parameters
Environment
Display Options
Scenario Presets
Doppler Formulas
What is the Doppler Effect?
The Doppler effect is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It was named after Austrian physicist Christian Doppler, who described the phenomenon in 1842. When the source and observer are moving toward each other, the observed frequency increases (blue shift). When moving apart, the observed frequency decreases (red shift).
Wave Source Motion
When a wave source moves toward an observer, the wavefronts are compressed in the direction of motion, creating a shorter wavelength and higher frequency. When moving away, the wavefronts are stretched, creating a longer wavelength and lower frequency. The formula is f' = f₀·v/(v ± vₛ), where vₛ is the source velocity (positive when moving away from observer, negative when approaching).
Observer Motion
When an observer moves toward a wave source, they encounter wavefronts more frequently, increasing the observed frequency. When moving away, they encounter wavefronts less frequently, decreasing the frequency. The formula is f' = f₀·(v ± vᵣ)/v, where vᵣ is the observer velocity (positive when moving toward source, negative when moving away).
Applications
The Doppler effect has numerous applications: radar and sonar speed measurement use frequency shifts to calculate velocity; medical ultrasound uses Doppler imaging to measure blood flow velocity; astronomy uses redshift and blueshift to measure stellar velocities and expand our understanding of the universe's expansion; emergency vehicle sirens change pitch as they approach and recede; weather radar uses Doppler shifts to detect wind patterns and storm rotation; and laser cooling uses Doppler cooling to slow atoms for quantum experiments.