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(C) For a spherical wave originating from a point source,the intensity $I$ is given by $I = \frac{P}{4\pi r^2}$,where $P$ is the power of the source.S

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$A/2$

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(C) For a spherical wave originating from a point source,the intensity $I$ is given by $I = \frac{P}{4\pi r^2}$,where $P$ is the power of the source.Since intensity $I$ is proportional to the square of the amplitude $A$ $(I \propto A^2)$,we have $A^2 \propto \frac{1}{r^2}$.This implies that the amplitude $A$ is inversely proportional to the distance $r$,i.e.,$A \propto \frac{1}{r}$.Given that at distance $r$,the amplitude is $A_1 = A$.At distance $r_2 = 2r$,the new amplitude $A_2$ will be:$\frac{A_2}{A_1} = \frac{r_1}{r_2} = \frac{r}{2r} = \frac{1}{2}$.Therefore,$A_2 = \frac{A}{2}$.

If the amplitude of waves at a distance $r$ from a point source is $A$,the amplitude at a distance $2r$ will be

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