Question

The beats are produced when there is a superposition of two sound waves which will have

• A. same amplitude and same frequency.
• B. different amplitude but same frequency.
• C. same amplitude but slightly different frequencies.
• D. different amplitude and different frequencies.

Hint:

The pipe becomes closed at the water end, and the air column is one third of the original length.

Answer 1

The Correct Option is C

Step 1: Wavelengths:
Open pipe fundamental: $\lambda = 2L$. Closed pipe fundamental: $\lambda' = 4\times\frac L3 = \frac{4L}{3}$.

Step 2: Frequency ratio:
$f\propto\frac1\lambda$, so $\frac{f'}{f} = \frac{2L}{4L/3} = \frac32$ (B).

Final Answer:
$\frac32f$. \[ \boxed{\frac{3}{2}f} \]