本题目来源于试卷: gc textbook chapter 12 Sound，类别为 通用国际物理
[问答题]
A noisy truck approaches youj * dx3tyq+btz 0,rb2 vyhyd43 from behind a building. Initially zubqc5/ gc+p 2 4ugoz.1zxg 1tyou hear it but cannot see it. When it emerges and you do see it, its sound is suddenly “brighter” — you hear more of the high-frequency noise. Explain. [Hint: See Section 11–15 on diffraction.z.gugo1 p tz241bc x5u+/z gcq]
参考答案: When
you first hear the truck, you cannot see it.
There is no straight line path from the truck to you. The sound waves that you are hearing are
therefore arriving at your location due to diffraction. Long wavelengths are diffracted more than
short wavelengths, and so you are initially only hearing sound with long
wavelengths, which are low-frequency sounds.
After you can see the truck, you are able to receive all frequencies
being emitted by the truck, not just the lower frequencies. Thus the sound “brightens” due to your
hearing more high frequency components.
本题详细解析:
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