Absorption means that a substance captures and transforms energy while concentration refers to the amount of a substance in a defined space.

If the concentration of solution is increased, then there are more molecules for the light to hit when it passes through.

**Formula to calculate concentration from absorbance.**

**Example:**

Suppose the molar absorptivity of Na Cl is 193L mol^{-1} cm^{-1} and the length of its light path is 5 cm, calculate the concentration if the absorbance is 200.

Therefore, the concentration is 0.21M.