A sound note of frequency 250 Hz and a wavelength 1.3 m is produced at a point near a hill. If the echo of the sound is received 1 second later at that point, how far away is the hill from the point?
A
248.7 m
B
261.3 m
C
162.5 m
D
131.3 m
Verified Correct Answer: C.
Step-by-Step Mathematical Solution
f = 250 Hz; λ = 1.3 m; t = 1 s; d = ?
v = fλ = 250 × 1.3 = 325 ms\(^{-1}\)
v = \(\frac{2d}{\text{t}}\)
∴ d = \(\frac{v \times t}{2}\) = \(\frac{(325 \times 1)}{2}\) = 162.5 m
Source: WAEC / JAMB / NECO Classroom Archive (Record #76378)