Beer's Law is described as if a light passes from a solution, the concentration of the solution is directly proportional to the absorbance of light by that solution.
Every element has a definite of absorbance of light.
In the testing of food, drugs or in medical testing, the light is passed from the sample.
Them transmitted light from these samples are measured. The difference between target light amount and transmitted light is the amount of absorbed light.
From this absorbed light value, we can identify an element in sample and its quantity.
Spectrophometry is based on this law.
