\(65 \mathrm{~m}\)
given: \(f=130 \mathrm{~Hz}, \lambda=2 \mathrm{~m}\)
\(t=0.5 \mathrm{~s} d=\) ?
\(\mathrm{v}=\mathrm{f \lambda}=130 \times 2=260 \mathrm{~m} / \mathrm{s}\)
but for echo \(v=\frac{2 d}{t}\)
\(\mathrm{d}=\frac{\mathrm{vt}}{2}=\frac{260 \times 0.5}{2}\)
\(\mathrm{d}=65 \mathrm{~m}\)