Question

A sound wave has a frequency of $1kHz$ and wave length $25cm$, to travel $2.2km$ it takes:

• A. $2\frac{3}{7}s$
• B. $80\frac{2}{5}min$
• C. $\frac{5}{4}min$
• D. $8\frac{4}{5}s$

Answer 1

The correct option is D $8\frac{4}{5}s$

As per the given data, we have,

Frequency$\left(f\right)$ = $1kHz=1000Hz$

Wavelength$\left(\lambda \right)$ = $25cm=0.25metres$

Distance$\left(s\right)$ = $2.2km=2200m$

We know that $time\left(t\right)=\frac{distance\left(s\right)}{speed\left(v\right)}$

$v=f\times \lambda$

$\therefore t=\frac{s}{f\times \lambda }$

$\therefore t=\frac{2200}{1000\times 0.25}=\frac{220}{25}=[\frac{200}{25}+\frac{20}{25}]=8\frac{4}{5}$ seconds