Optics 7 Question 30
31. A point source emits sound equally in all directions in a non-absorbing medium. Two points $P$ and $Q$ are at a distance $9 m$ and $25 m$ respectively from the source. The ratio of amplitudes of the waves at $P$ and $Q$ is
$(1989,2 M)$
True / False
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Solution:
- $\quad I \propto \frac{1}{r^{2}} \quad$ (in case of point source)
and $I \propto A^{2}$
$$ \begin{array}{ll} \Rightarrow & A \propto \frac{1}{r} \\ \text { or } & \frac{A _1}{A _2}=\frac{r _2}{r _1}=\frac{25}{9} \end{array} $$
