多普勒效应
声源在空气中运动,前方波被挤短,后方波被拉伸,是1842年奥地利物理学家约翰.克里琴斯.多普勒首先提出.此为多普勒效应,一般人并不陌生.鸭子在平静水面嬉戏,泛起圈圈圆波匀速向远处扩散.鸭子游弋,因与前方波同向,与后方波反向运动,前后方波幅就发生了变化,鸭子也偏离了圆的中心
With an observer stationary relative to the medium,if a moving source is emitting waves with an actual frequency(in this case,the wavelength is changed,the transmission velocity of the wave keeps constantnote that the transmission velocity of the wave does not depend on the velocity of the source),then the observer detects waves with a frequencygiven by