A plane sound wave of frequency 85.5Hz and velocity 342ms−¹ is reflected from a vertical wall. At what distance from the wall does the wave have antinode?

A. 2m
B. 4m
C. 1m
D. 3m

Correct Answer:

Option C = 1m

Explanation

If F = 85.5Hz, V = 342ms−¹,
Then wavelength = V/F = 342/85.5 = 4m

Then if wavelength = 4m
=> wavelength/2 = 4/2 = 2m = NN,
Thus NA = wavelength/4 = 4/4 = 1m.