Letter | Published:

Doppler's Principle

Naturevolume 43page80 (1890) | Download Citation



THIS subject was referred to in NATURE some months ago, but, although the question is comparatively simple, there is one point of some importance which was not then brought out and to which I have never seen any reference. The change in pitch is, of course, due to the change in the rate at which the cycles of disturbance which constitute the wave-motion fall upon the ear. To determine this charge of rate, it is necessary to consider (1) the space occupied by each cycle; (2) the relative velocity of the wave-motion and the observer. Consideration (1) is connected with the velocity of the source of sound, and if wave-length be defined as the shortest distance between two vibrating particles in the same phase, then the space occupied by each cycle may be called the wave-length. If, however, wave-length be defined as the distance which the wave-motion travels through the medium during the “period” of vibration of the sounding body, then the wave-length so defined is unaffected by the motion of the sounding body. It is in connection with this point that there is generally some ambiguity in the usual terms of explanation.

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  1. Cambridge

    • R. W. STEWART


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