A.y=Acos[w(t+1/u)+φ0] B.y=ACOS[w(t-1/u)+φ0] C.y=Acos[wt+1/u+φ0] D.y=Acos[wt-1/u+φ0]
A.2Hz B.4Hz C.6Hz D.8Hz
A.波長(zhǎng)為0.5m B.波長(zhǎng)為0.05m C.波速為25m/s D.波速為5m/s