If you can see this message Flash may not be working in your browser
Please see http://nrich.maths.org/techhelp/#flash to enable it.
The molar extinction coefficient $\epsilon(\lambda)$ of a chemical measures theintrinsic property of how the chemical absorbs light of wavelength $\lambda$. When such light passes through a homogeneous solution of the chemical, the absorbance $A$ is measured by the Beer-Lambert law $A=\epsilon(\lambda) cL$, where $c$ is the concentration of the chemical and $L$ is the path
length of the light passing through the solution. Recall that 1 katal = 1 mole per second.
With thanks to Keith Johnstone for providing the template for this question.