The intensity of sound from a radio at a distance of $2$ metres from its speaker is $1 \times {10^{ - 2}}\mu \;W/{m^2}.$ The intensity at a distance of $10$ meters would be
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(c) $I \propto \frac{1}{{{r^2}}} \Rightarrow \frac{{{I_2}}}{{{I_1}}} = \frac{{r_1^2}}{{r_2^2}}$
==> $\frac{{{I_2}}}{{1 \times {{10}^{ - 2}}}} = \frac{{{2^2}}}{{{{10}^2}}} = \frac{4}{{100}}$
==> ${I_2} = \frac{{4 \times {{10}^{ - 2}}}}{{100}}$ = $4 \times {10^{ - 4}}\;\mu \;W/{m^2}$
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