[单选题]
A tuning fork is held above a
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pos 4ggciiy/,5 v-3 hcter as shown in the diagram below.
Initially, the pipe is fully immersed in the water. The pipe and the vibrating tuning fork are slowly lifted upward from the surface of the water, creating an air column inside the pipe above the water surface.
A maximum intensity of the sound is first heard when the air column reaches a length $a$ and again at length $b$.
Which of the following statements are correct about the lengths $a$ and $b$, and the wavelength λ?
I.$b=3a$
II.$ λ=\frac{3b}{4}$
III.$ λ=4a$
A. Only $I$
B. Only $III$
C. $I$ and $III$
D. $I$, $II$, and $III$
参考答案:
C
本题详细解析:
Explanation：
The first harmonic will be found when length is equal to 44λ, which is $a$.
The next harmonic at b, is when the length is equal to $\frac{3λ}{4}$.
Therefore, statements I and III are correct.
