how can I rearrange this formula involving an exponential?

Question

I have this equation

$p = r^l$

I know $p$ and $r$ and I would like to solve for $l$, how can I rearrange this formula to achieve this?
I initially came up with:

$l = \sqrt[r]{p}$

( $l$ is the $r$th root of $p$) but my intuition says this is wrong and after putting in numbers - I know this is wrong - how can I rearrange to solve for $l$?

Answer 1

This is what the logarithm is for. We say $l=\log_r(p)$.