Answer
The intensity will quadruple.
Work Step by Step
$d = 10$
$s= 10$
$sd^2=k$
$10*10^2 = k$
$1000 = k$
$d=5$
$s*5^2=1000$
$25*s=1000$
$s = 40$
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.