Answer
$1\times10^{-6}m$
Work Step by Step
$$RP=\frac{1.22\lambda f}{D}=\frac{(1.22)(550\times10^{-9}m)(9mm)}{5mm}$$
$$RP=1.21\times10^{-6}m\approx 1\times10^{-6}m$$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.