# Is Beer-Lambert law also valid for fluorescence and luminescence?

When I measure optical density in a microplate reader the absorbance is proportional to the concentration and the height of the liquid. Is Beer-Lambert law also valid for fluorescence and luminescence?

Let's say I prepare a fluorescent solution and measure e.g. the signal of 100 μL and of 50 μL. Do I get the half signal for 50 μL?

No the Beer Lambert law ($$I_{trans}=I_0\exp(-\epsilon[C]L)$$) does not apply as this shows that the transmitted light intensity decreases exponentially with concentration as it passes through a solution.