What does transmittance measure in a spectrophotometric analysis?

Transmittance is specifically defined as the ratio of the intensity of light that passes through a sample to the intensity of the incident light. In spectrophotometric analysis, measuring transmittance allows researchers to determine how much of the light is transmitted through the sample being analyzed. High transmittance indicates that a large portion of light is passing through the sample, while low transmittance suggests that more light is being absorbed or reflected by the sample. This measurement is essential for determining concentration and other properties of the material being studied, as it directly relates to how a substance interacts with light.

The other options refer to different aspects of light interaction with materials. The amount of light absorbed by a sample relates to absorbance, which is distinct from transmittance. Reflectance involves light that is bounced off the surface of a sample, not the light that passes through. The wavelength of light absorbed pertains to the specific energies at which a substance interacts with light but does not define transmittance itself. Thus, the focus on transmittance as the measure of light that passes through a sample is fundamental to understanding how spectrophotometry works.