Question

Two sources of sound $S_1$ and $S_2$ vibrate at the same frequency and are in phase. the intensity of sound detected at a point $P$ is $I_0$ if $\theta ={45}^{\circ }$, what will be the intensity of sound reaching $P$ if one of the sources is switched off. What will be the intensity if $\theta ={60}^{\circ }$

• A. $\frac{I_0}{4},\frac{I_0}{8}$
• B. $\frac{I_0}{4},\frac{I_0}{2\sqrt{2}}$
• C. $\frac{I_0}{4},\frac{I_0}{4}$
• D. $\frac{I_0}{4\sqrt{2}}\frac{I_0}{8}$

Answer 1

Answer: (C)

$\frac{I_0}{4},\frac{I_0}{4}$

since the wave reaches in phase $I_0=4I$
$I_{max}a(y_{01}+y_{02}{)}^2=(2y_{02}{)}^2=4y_{02}^2=4I$
$\therefore I=\frac{I_0}{4}$ It is independent of $\theta$