How does a spectrophotometer function in water quality analysis?

A spectrophotometer functions in water quality analysis by measuring the intensity of light absorbed by water samples at specific wavelengths. This technique is vital because the absorption of light can provide information about the concentration of various substances within the water, including organic and inorganic compounds. Each substance has a unique absorption spectrum, meaning it absorbs light at specific wavelengths. By comparing the amount of light incident on the sample to the amount of light transmitted through it, analysts can determine the concentration of the substance of interest, which is essential for assessing water quality.

The other options represent methods or tools that do not accurately describe the core function of a spectrophotometer. For instance, measuring pH levels involves using pH meters that rely on electrochemical properties rather than light absorption. Analyzing microbial content typically requires different methods, such as culture techniques or microscopy, rather than optical measurement. Detecting temperature variations is also unrelated, as temperature assessment requires thermometric instruments. Thus, the function of a spectrophotometer is specifically aligned with light absorption measurements, making the second option the correct choice in the context of water quality analysis.