A bat can hear sound of frequencies up to 120 kHz. Determine the minimum wavelength of sound which it can hear. Take speed of sound in air to be 344ms^-1   

$$\begin{gathered} \mathrm{Given}, \mathrm{f}=120\mathrm{kHz}=120\times {10}^3\mathrm{Hz},\mathrm{V}=344{\mathrm{ms}}^{-1} \\ \text{ From relation }\mathrm{V}=\mathrm{f\lambda } \\ \text{ Wavelength }\mathrm{\lambda }=\frac{\mathrm{V}}{\mathrm{f}}=\frac{544}{120\times {10}^3} \\ =2.87\times {10}^{-3}\mathrm{m}(\text{ or }2.87) \\ \mathrm{i}.\mathrm{e}., \mathrm{the} \mathrm{bat} \mathrm{can} \mathrm{hear} \mathrm{sound} \mathrm{of} \mathrm{minimum} \mathrm{wavelength} 2.87 \mathrm{mm} \end{gathered}$$