Question

In Quincke's experiment the sound detected is changed from a maximum to a minimum when the sliding tube is moved through a distance of 2.50 cm. Find the frequency of sound if the speed of sound in air is 340 m s⁻¹.

Answer 1

Given:
Speed of sound in air v = 340 ms⁻¹
Distance moved by sliding tube = 2.50 cm
Frequency of sound f = ?

$$\begin{gathered} \mathrm{Distance}\mathrm{between}\mathrm{maximum}\mathrm{and}\mathrm{minimum}: \\ \frac{\mathrm{\lambda }}{4}=2.50\mathrm{cm} \\ \Rightarrow \mathrm{\lambda }=2.50\times 4=10\mathrm{cm}={10}^{-1}\mathrm{m} \end{gathered}$$

As we know,
v = f$\lambda$.

$$\begin{gathered} \mathit{\therefore }\mathit{}f=\frac{v}{\mathrm{\lambda }} \\ \Rightarrow f=\frac{340}{{10}^{-1}}=3400\mathrm{Hz}=3.4\mathrm{kHz} \end{gathered}$$

Therefore, the frequency of the sound is 3.4 kHz.