## Algebra: A Combined Approach (4th Edition)

When $d$ is doubled, the intensity is four times smaller.
$I=\frac{k}{d^2}$ When $d$ is doubled, $\frac{k}{(2d)^2}=\frac{k}{4d^2}$ Since $\frac{k}{d^2}=I$, $\frac{k}{4d^2}=\frac{I}{4}$ When $d$ is doubled, the intensity is four times smaller.