Which statement concerning optical density according to Beer's Law is true?

According to Beer's Law, the relationship between absorbance (A) and concentration (c) of a solution is a direct one, expressed in the formula A = εlc, where A is absorbance, ε is the molar absorptivity, l is the path length through which the light travels in the sample, and c is the concentration of the solution. Since optical density is another term for absorbance, it follows that optical density is also directly proportional to concentration. This means that as the concentration of a solution increases, the optical density will also increase, assuming constant path length and molar absorptivity.

The other statements do not accurately reflect the relationship described by Beer's Law. The relationship described in the correct option reflects the fundamental basis for quantitative analysis in spectrophotometry, making it crucial for laboratory measurements involving concentration determination.