AALSO Water Quality Level 1 Practice Test

Absorption spectroscopy is an analytical method that uses how materials absorb light at different wavelengths to identify and quantify substances. When light shines through a sample, molecules absorb specific wavelengths based on their electronic structure, so the light that passes through has a distinct pattern of absorbed versus transmitted wavelengths. This pattern, or spectrum, serves as a fingerprint that can identify the substance when compared to reference spectra. For quantification, the amount of light absorbed at a particular wavelength is related to the concentration of the absorbing species through the Beer-Lambert law, which states that absorbance equals the molar absorptivity times the path length times the concentration. In practice, you measure the sample’s absorbance, often after calibrating with standards, and deduce both the identity (from the spectrum) and the amount (from the absorbance value). This approach underpins UV-Vis spectroscopy and requires a light source, a means to select or scan wavelengths, a sample holder, and a detector.

The other options describe different techniques: emission spectroscopy measures light emitted by excited samples rather than what is absorbed; separating mixtures by evaporation refers to distillation; determining pH involves acid-base indicators or a pH meter, not absorption spectra.