Question

Suppose you have a light bulb that emits 200 watts of visiblelight.How far away would you have to put the light bulb forit to have thesame apparent brightness as Alpha Centauri A in oursky? (Hint: Use200 watts as L in the inverse square law for light,and use theapparent brightness given above for Alpha Centauri A.Then solve forthe distance.)

Use the inversesquare law.

I got the correctluminosity, I just don't know how to solvefor the distance. Helpplease!