Transmittance

Definition

Transmittance is the measure of the fraction of light that passes through a sample. It quantifies how much light is not absorbed by the sample.

5 Must Know Facts For Your Next Test

1. Transmittance can be calculated as the ratio of transmitted light intensity to the incident light intensity.
2. It is usually expressed as a percentage, known as percent transmittance (%T).
3. In microbiology, transmittance is used in spectrophotometry to determine the concentration of microorganisms in a sample.
4. Higher transmittance indicates lower absorbance and hence, fewer microorganisms or particles in the sample.
5. The Beer-Lambert Law relates transmittance to absorbance and concentration of absorbing molecules.

Review Questions

• How is transmittance measured in a laboratory setting?
• Why might high transmittance indicate low microorganism concentration in a sample?
• What relationship does the Beer-Lambert Law describe concerning transmittance?

Related terms

Absorbance:

A measure of the amount of light absorbed by a sample.

Spectrophotometry: A technique used to measure how much light is absorbed by a chemical substance.

Beer-Lambert Law: A linear relationship between absorbance and concentration of an absorbing species.