Calculate frequency shifts due to the Doppler effect when sources and observers are in relative motion. Perfect for physics students, engineers, and researchers studying wave phenomena.
Doppler Effect Calculator
Speed of sound in air at 20°C: 343 m/s
Positive: moving toward observer
Positive: moving toward source
Results
Observed Frequency
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Frequency Change
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Percentage Change
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Wavelength Change
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Wave Visualization
Blue: Original wave, Red: Doppler-shifted wave
Doppler Effect Theory
The Doppler Formula
The observed frequency is given by:
$$f' = f \frac{v \pm v_o}{v \mp v_s}$$
Where:
f' = observed frequency
f = source frequency
v = wave speed
v_o = observer velocity
v_s = source velocity
Sign Conventions
Observer velocity: Positive when moving toward source
Source velocity: Positive when moving toward observer
The Doppler effect is the change in frequency of a wave when there is relative motion between the source and observer. When the source moves toward the observer, waves are compressed, resulting in higher frequency. When moving away, waves are stretched, causing lower frequency. This effect occurs with all types of waves including sound, light, and radio waves.
For source velocity: positive means moving toward the observer, negative means moving away. For observer velocity: positive means moving toward the source, negative means moving away. When source and observer approach each other, frequency increases. When they move apart, frequency decreases.
Doppler effect calculations are used in radar speed detection, medical ultrasound imaging, weather radar systems, astronomical observations to measure stellar velocities, blood flow monitoring, sonar systems, and satellite communications. The effect is also responsible for the changing pitch of sirens as emergency vehicles pass by.