Which statement accurately describes a spectrophotometer's function?

Which statement accurately describes a spectrophotometer's function?

• A. It measures the amount of light at a specific wavelength passing through a medium using cuvettes
• B. It heats samples to a set temperature
• C. It separates DNA fragments by size
• D. It provides qualitative color changes of indicators

Answer: (A)

A spectrophotometer works by sending light at a specific wavelength through a sample held in a cuvette and measuring how much of that light passes through. The instrument then reports the transmitted light, which is converted into absorbance. Because absorbance at a given wavelength is related to how much solute is present (the concentration), this allows you to quantify how much of a colored substance or nucleic acid/protein is in the sample. The cuvette provides a uniform path length for the light, ensuring accurate measurements. This function is distinct from heating samples, which is what a heater does, or from separating DNA fragments by size, which is done by gel electrophoresis. It’s also more precise than simply noting a qualitative color change, because it yields a numeric absorbance value that can be tied to concentration with proper calibration.

A spectrophotometer works by sending light at a specific wavelength through a sample held in a cuvette and measuring how much of that light passes through. The instrument then reports the transmitted light, which is converted into absorbance. Because absorbance at a given wavelength is related to how much solute is present (the concentration), this allows you to quantify how much of a colored substance or nucleic acid/protein is in the sample. The cuvette provides a uniform path length for the light, ensuring accurate measurements. This function is distinct from heating samples, which is what a heater does, or from separating DNA fragments by size, which is done by gel electrophoresis. It’s also more precise than simply noting a qualitative color change, because it yields a numeric absorbance value that can be tied to concentration with proper calibration.