### Q. ** Beer's law states that ... **

**Answer is C)** Lambert's law states that the proportion of light absorbed by a material is independent of the intensity of the incident radiation. Beer's law states that the * absorbance* of a sample is

*to the*

**directly proportional***. The combination of these two laws gives the expression: A = ε c l*

**concentration of the absorbing species**where A is the absorbance, ɛ is the molar absorption coefficient, c is the concentration and l is the path length. The Beer-Lambert law brings together into an equation that which relates the absorbance with the sample concentration (c), the sample thickness (path length, I) and the inherent absorption capability (molar absorptivity, ɛ). The size of the molar absorptivity (or extinction coefficient in the old terminology) is an indication of how sensitive an analysis will be, since, the more a molecule is capable of absorbing light, the smaller the amount of the material we will be able to detect. Molar absorptivity has the units M-1 cm-1, since the product ɛcl must be dimensionless.

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