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Dopplers Principle Applied to Light Waves

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-485

2025-12-25

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Doppler's Principle Applied to Light Waves.The position of the dark lines of the spectrum is invariable only when the distance between the source of light and the observer is fixed. If this distance is regularly diminishing, the wave length corresponding to a given line diminishes, and if it is increasing, the wave length increases.

If the spectrum of a star is examined, and it is found that the C line, for instance, is located at the right of the position of that line in the solar spectrum, as the lighter line in Fig. 1, the explanation is that the star is moving toward us and thus shortening the wave length that produces the line. If the displacement is toward the red end of the spectrum, then the star is receding from us. Since the velocity of the star determines the amount of this displacement, a measurement of this amount can be used as a basis for calculating the velocity of the star's motion.