Question

Two speakers A and B are placed 1 m apart, each produces sound waves of frequency 1800 Hz in phase. A detector moving parallel to the line joining the speakers at a distance of 2.4 m away detects a maximum intensity at O and then at P. Speed of the sound wave is:

• A. 330 ms${}^{-1}$
• B. 360 ms${}^{-1}$
• C. 350 ms${}^{-1}$
• D. 340 ms${}^{-1}$

Answer 1

The correct option is B 360 ms${}^{-1}$

At point O path difference is zero.

At point P path difference, $=AP-BP=\sqrt{1^2+{2.4}^2}-2.4=0.2m$

Path difference from first bright to second bright equal to $\lambda$

Path Difference $=\lambda =0.2$

Velocity, $v=\lambda \nu =0.2\times 1800=360m{s}^{-1}$

Hence, velocity is $360m{s}^{-1}$.