[单选题]
A tuning fork is held above a hollow pipe which is in
bu:+x1ymyvqos am 68b-pi6 m,a long cylinder filled wi
or2q8(9+i dgqtats0qt s g296vq axg6th water as shown in the
(8qs9+t220aor6v gx9gi as6qtt qdgqdiagram 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.
