Fill in the blanks:
$(i)$ For humans,the minimum wavelength of a sound wave in the audible range is nearly ...... .
$(ii)$ Only ...... waves can be propagated by a fluid medium.
$(iii)$ The distance travelled by a travelling wave having wavelength $\lambda$ and periodic time $T$,in one second is ...... .

(A) $(i)$ Given the speed of sound $v = 332 \text{ m/s}$ and the maximum audible frequency $f_{\max} = 20000 \text{ Hz}$.
Using $v = f \lambda$,we have $\lambda_{\min} = \frac{v}{f_{\max}} = \frac{332}{20000} = 0.0166 \text{ m} = 1.66 \text{ cm}$.
$(ii)$ Fluids (liquids and gases) do not support shear stress,therefore only longitudinal waves can propagate through them.
$(iii)$ The distance travelled by a wave in one second is equal to its speed $v$.
Since $v = \frac{\lambda}{T}$,the distance travelled in one second is $\frac{\lambda}{T}$.