Rami Arieli: " The Laser Adventure" Chapter 2.3 page 2
Example 2.2: Absorption Coefficient (a)

Calculate the absorption coefficient (a) of materials which transmit 50% of the intensity of the incident radiation on a 10 [mm] width, to the other side.

Solution to example 2.2:
Using the exponential absorption law:

a = 1/x * ln(1/T) = 1/1 * ln(1/0.5) = 0.69 [cm-1]

Results from the exponential absorption law: