Question

Sound of wavelength $\lambda$ is received from two coherent sources of sound $S_1$ and $S_2$ by a detector at $P$. Intensity of the sound received is $16l$. If the intensity received at $P$ is $l$ on switching off only $S_1,$ the intensity received at $P$ on switching off only $S_2$ is

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• A. $15l$
• B. $\sqrt{15}l$
• C. $9l$
• D. $3l$

Answer 1

The correct option is C $9l$

Path difference $=1000\lambda$
$\Rightarrow$ Maxima is formed at $P$
$\Rightarrow 16l=(\sqrt{l}+\sqrt{l^{\prime }}{)}^2$
$\Rightarrow I^{\prime }=9l$