本题目来源于试卷: Wave Behavior C.5 Doppler Effect，类别为 IB物理学
[单选题]
A train is traveling ao; 8 kyd6dl5qk:ijlx )9gu qq1kk9hm*5inmq6e) 3ph at $30\,ms^{−1}$ towards a stationary observer. It sounds a horn of frequency 450 Hz.
Which of the following statements is true about the observed frequency compared with the emitted frequency as the train approaches?
A. Observed frequency compared to emitted frequency is Lower ; Change in observed frequency over time is No change
B. Observed frequency compared to emitted frequency is Higher ; Change in observed frequency over time is Increases
C. Observed frequency compared to emitted frequency is Lower ; Change in observed frequency over time is Decreases
D. Observed frequency compared to emitted frequency is Higher ; Change in observed frequency over time is No change
参考答案: D
本题详细解析:
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