3. A sound source emits a sound wave of frequency f. If the source is moving toward a stationary observer at one third (i.e., 1/3) of the speed of sound, what frequency does the observer observe?
(A) 3f
(B)
(C) f
(D)
(E)
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統計: 尚無統計資料
統計: 尚無統計資料