First law of light absorption

 Each thin layer of constant thickness of a homogeneous environment absorbs an identical part of incident radiation

or:

 The part of the light which is absorbed by a homogeneous environment, is directly proportional to a thickness of an absorbing layer:

Second law of light absorption

The part of the absorbed radiation is proportional to number of absorbing particles in volume of a solution, that is concentration

Bouguer-Lambert-Beer law

Reduction of intensity of light which has passed through a layer of light-absorbing substance is proportional concentration of this substance and a thickness of a layer