How do you determine percent transmittance from absorbance?

Percent transmittance can be determined from absorbance using the formula: %T = 100 * 10^-A, where A is the absorbance.

In more detail, the relationship between absorbance (A) and transmittance (T) is logarithmic, as defined by the Beer-Lambert Law. This law states that the absorbance of a solution is directly proportional to its concentration and the path length of the light through the solution. In other words, the more concentrated a solution is, or the longer the path of light through the solution, the more light will be absorbed and the less will be transmitted.

The formula %T = 100 * 10^-A is derived from the Beer-Lambert Law. Here, %T represents the percent transmittance, or the percentage of light that passes through the solution and reaches the detector on the other side. A is the absorbance, which is a measure of the amount of light absorbed by the solution.

To calculate percent transmittance from absorbance, you simply plug the absorbance value into the formula and perform the calculation. For example, if the absorbance is 0.5, the percent transmittance would be 100 * 10^-0.5 = 31.62%.

It's important to note that percent transmittance can range from 0% (no light transmitted) to 100% (all light transmitted), while absorbance can theoretically range from 0 (all light transmitted) to infinity (no light transmitted). However, in practical terms, absorbance values typically fall between 0 and 2.

Understanding the relationship between absorbance and transmittance is crucial in many areas of chemistry, particularly in spectroscopy where it is used to determine the concentration of a substance in a solution. By measuring the amount of light that is absorbed or transmitted by a solution, chemists can infer the concentration of the solute, providing valuable information about the solution's composition.