CHANGING DIAMETER

A source produces a sound wave that is tightly focused into a beam with a circular cross$-$section.

For each case, determine the power ratio and the area ratio, then use them to find the intensity ratio.

$($a$)$ Suppose you make the beam diameter $8$ times bigger, without changing the source power?

$\frac{I_f}{I_i}=$

$($b$)$ What if you make the beam diameter $8$ times smaller, without changing the source power?

$\frac{I_f}{I_i}=$

$$

$$

$($c$)$ What if you make the source power $4\mathrm{.}5$ times smaller and the beam diameter $8$ times smaller?

$\frac{I_f}{I_i}=$

$$

$==$

$$