MHT CET · Physics · Waves and Sound

Two open pipes of different lengths and of same diameter in which the air column vibrates with fundamental frequencies ‘ $n_{1}$ ’, and ‘ $n_{2}$ ’ respectively. When both pipes are joined to form a single pipe, its fundamental frequency will be

A $\frac{n_{1} + n_{2}}{n_{1} n_{2}}$
B $\frac{n_{1} n_{2}}{2 n_{2} + n_{1}}$
C $\frac{2 n_{2} + n_{1}}{n_{1} n_{2}}$
D $\frac{n_{1} n_{2}}{n_{1} + n_{2}}$

Verified Solution

Answer & Solution

Correct Answer

(D) $\frac{n_{1} n_{2}}{n_{1} + n_{2}}$

Step-by-step Solution

Detailed explanation

n_{1} = \frac{v}{2 l_{1}}; n_{2} = \frac{v}{2 l_{2}}

∴ n = \frac{v}{2 (r + l_{2})} = \frac{v}{2 r + 2 l_{2}}

n = \frac{v}{\frac{v}{n_{1}} + \frac{v}{n_{2}}} = \frac{n_{1} n_{2}}{n_{1} + n_{2}}

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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Two open pipes of different lengths and of same diameter in which the air column vibrates with fundamental frequencies ‘ n1 ’, and ‘ n2 ’ respectively. When both pipes are joined to form a single pipe, its fundamental frequency will be

Step-by-step Solution

Two open pipes of different lengths and of same diameter in which the air column vibrates with fundamental frequencies ‘ $n_{1}$ ’, and ‘ $n_{2}$ ’ respectively. When both pipes are joined to form a single pipe, its fundamental frequency will be