Question

​​The maximum length of a closed pipe that would produce just audible sound is (V_s=336 m/s)
a) 4.2 cm b) 4.2 m c) 4.2 mm d) 1 cm

Answer 1

Dear Student,

$$\begin{gathered} \mathrm{for}\mathrm{closed}\mathrm{pipe}, \\ \mathrm{n}=\frac{\mathrm{v}}{4\mathrm{l}} \\ \mathrm{frequency}\mathrm{of}\mathrm{just}\mathrm{audible}\mathrm{sound},\mathrm{n}=20\mathrm{Hz} \\ \mathrm{v}=336\mathrm{m}/\mathrm{s} \\ \mathrm{l}=\frac{\mathrm{v}}{4\mathrm{n}} \\ \mathrm{l}=\frac{336}{4\times 20}=4.2\mathrm{m} \end{gathered}$$