Doppler Effect: Frequency shift from a moving source or observer. This free calculator solves for Observed frequency, speeds and shows every step.
Relative motion between a wave source and an observer compresses or stretches the waves, raising or lowering the observed frequency — the rising-then-falling pitch of a passing siren. For light, the same effect gives the redshift of receding galaxies and the basis of police radar.
Sign convention used here: enter a speed as positive when that body is moving toward the other, and negative when moving away.
Siren f = 700 Hz, source approaching at v_s = 30 m/s, still observer, v = 343 m/s. f′ = 700·343 / (343 − 30) ≈ 767 Hz.
Police and weather radar, sonar, medical Doppler ultrasound, astronomy (galactic redshift), speed cameras.
Doppler Effect uses the formula f′ = f·(v + v_o) / (v − v_s). Frequency shift from a moving source or observer.
Choose which variable to solve for, enter the values you know (in any supported unit), and the calculator substitutes them into f′ = f·(v + v_o) / (v − v_s) and shows every step of the working. It can solve for Observed frequency, speeds.
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