[Kids_On_Coffee]

I'm using Beer's Law for finding an extinction coefficient (ε) for p-nitrophenol at λmax. Is my answer going to be unit-less? also, in Beer's Law, the path length is in cm. is this the length of the cuvette? or do i need to convert the wavelength in nm to cm?  Thanks in advance, Cheers!

[Arkcon]

When you put in all the known values, with their units, you''l be able to cancel out units, and you'll know the answer.  And the path length, is just what its says -- the length of the path the light took to give the experimental absorbance value.  Do you think it is the length of the cuvette in question, from what you know about the layout of the instrument?

[Babcock_Hall]

I have seen beginning students try to put λ the wavelength into Beer's law where A the absorbance should be.  Perhaps the explanation is that b the path length being in units of length and λ also being in units of length is a point of confusion.  The two quantities are otherwise unrelated, however.