Lamberts Law

 Lambert showed that each unit length of material through

 which light passes absorbs the same fraction of the incident or entering 

light and compares the relation between the incident light (Io) and the transmitted light (IT) for various thicknesses t.

log e (Io/IT) = mue(u)*t

Where: I is the intensity of light; t is the thickness of the substance;  the absorption coefficient 

log base 10 (Io/IT) = (mue(u)/2.303)*t = epselon (e)*t

Where  epeleson(e) the extinction coefficient is generally defined as the reciprocal of the thickness 

(t in cm) required in order to reduce the intensity of the incident light to its original intensity.