Sensitive Light meter and meter stick to measure distance

[phyzwiz69]

1. Suppose you are on the bank of a river at night. Opposite you on the other bank is a street light. You have a sensitive light meter and a meter stick. How wold you determine the distance across the river?

 

[Redbelly98]

You'll have to provide your own thoughts or attempt at a solution before receiving help.

What equations dealing with light sources are in your recent class notes, or textbook reading?