Re: definition of Beer's law - basis 10 or e Log?


"Matt" <matthroth@xxxxxxxxx> wrote in message
news:c44deaab-9f8f-4cbb-9934-412c4876b974@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi all,

I noticed there are different definitions of Beer's law. In analytical
chemistry it is often defined with the basis 10:

I/I0 = 10^(-aL)

where a is the absorption (extinction) coefficient.

Then in engineering/photonics there seems to be the definition based
on the natural log

I/I0 = e^(-aL)

so which one is it? I am working with absorption coefficients in laser
crystals and some books use the basis e. On the other hand crystal
manufactures don't specify which absorption coefficient they mean -
basis 10 or e - for example for the absorption in 1% doped Nd:YVO4,
where a=41cm^-1.


It is both, just as you have discovered, Matthias. Almost certainly the
laser crystal manufacturers are using the natural logarithm, but you always
have to be aware of this issue. You should ask them.

Mostly, it is chemists doing spectroscopy who use base 10. That means,
however, that published absorption coefficients of things that chemists look
at tend to be base 10.


.

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