Relativistic Doppler Shiftwhere the plus sign is taken for waves traveling away from the observer. For light and other electromagnetic waves, the relationship must be modified to be consistent with the Lorentz transformation and the expression becomes Here v is the relative velocity of source and observer and v is considered positive when the source is approaching.

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Doppler Effect

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Fractional Wavelength ChangeThe fractional wavelength change is defined as the z parameter for characterizing red shifts:

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Doppler Frequency

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