the Doppler effect
noun/ðə ˈdɒplər ɪfekt/
/ðə ˈdɑːplər ɪfekt/
[singular] (physics)- the way that sound waves, light waves, etc. change in frequency depending on the direction that the source is moving in relative to the person who is observing
多普勒效应(即声波、光波等按声源、光源等相对于观察者的传播方向的变化而变化)