Which instrument measures the intensity of light absorbed by a chemical substance, often used to analyze nutrient concentrations?

• A. Hand Lens
• B. Micropipette
• C. Graduated Cylinder
• D. Spectrophotometer

Answer: (D)

Measuring how much light a chemical substance absorbs lets us determine its concentration. A spectrophotometer shines light of a specific wavelength through a liquid sample and measures how much light is absorbed (or how much passes through). Because absorbance relates to concentration, you can quantify nutrient levels by comparing the reading to known standards. In practice, the sample sits in a cuvette, and the instrument returns an absorbance value that you convert to concentration using a calibration curve. The other tools aren’t designed for this purpose: a hand lens only enlarges details, a micropipette transfers precise volumes, and a graduated cylinder measures volume. So the instrument used to measure light absorption to analyze nutrient concentrations is the spectrophotometer.