Beer's Law states that the concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to transmitted light. Which statement is correct?

• A. The concentration is directly proportional to the amount of light absorbed.
• B. The concentration is directly proportional to transmitted light.
• C. The concentration is inversely proportional to the amount of light absorbed.
• D. The concentration is independent of light absorption.

Answer: (A)

Beer's Law shows how the amount of light absorbed by a solution changes with how much solute is present. The key relationship is A = εlc, where absorbance A increases with concentration c (assuming path length l and molar absorptivity ε are constant). Since absorbance grows as concentration grows, concentration is directly proportional to the amount of light absorbed. Transmitted light behaves oppositely: more absorption means less light passes through, so concentration is inversely related to transmitted light. Therefore, the correct statement is that concentration is directly proportional to the amount of light absorbed.