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11.Dual Nature of Radiation and matter
hard
A point source is emitting sound waves of intensity $16 \times 10^{-8} \mathrm{Wm}^{-2}$ at the origin. The difference in intensity (magnitude only) at two points located at a distances of $2 \mathrm{~m}$ and $4 \mathrm{~m}$ from the origin respectively will be______ $\times 10^{-8} \mathrm{Wm}^{-2}$
A
$3$
B
$2$
C
$1$
D
$5$
(JEE MAIN-2024)
Solution
Correct answer is : $3$
We know for point source, $I \propto \frac{1}{r^2}=\frac{K}{4 \pi r^2}$
$r_1=2 m, r_2=4 m=2 r_1 $
$I_0=16 \times 10^{-8} W / m ^2$
at $2 m$,
$I_1=\frac{I_0}{(2)^2}=\frac{16 \times 10^{-8}}{4} $
$I_1=4 \times 10^{-8} $
$ I_2=\frac{I_0}{4_2}=\frac{16 \times 10^{-8}}{16}=10^{-8} $
$\left|I_2-I_1\right|=3 \times 10^{-8} W / m ^2, x=3$
Standard 12
Physics
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