The appropriate change in frequency when the suns rays approaches an observer is referred to as
A change in the observed frequency of a wave, as of sound or light, occurring when the source and observer are in motion relative to each other, [ with the frequency increasing when the source and observer approach each other and decreasing when they move apart. The motion of the source causes a real shift in frequency of the wave, while the motion of the observer produces only an apparent shift in frequency. Also called Doppler shift.
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