Doppler Effect - for stationary observer
The Doppler effect is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. When the speeds of source and the receiver relative to the medium are lower than the velocity of waves in the medium, there is a relationship between observed frequency and emitted frequency depended on the velocity of waves in the medium. The velocity of the receiver relative to the medium is positive if the receiver is moving towards the source (and negative in the other direction).
With an observer stationary relative to the medium, if a moving source is emitting waves with an actual frequency f_0 (in this case, the wavelength is changed, the transmission velocity of the wave keeps constant — note that the transmission velocity of the wave does not depend on the velocity of the source), then the observer detects waves with a frequency f given by the formula shown here.Related formulas
|f||observed frequency (Hz)|
|f0||emitted frequency (Hz)|
|c||velocity of waves in the medium (m/s)|
|vs||velocity of the source relative to the medium (m/s)|