Logarithmic Vs. Directly Proportional Measurements
The amount of light transmitted through a material diminishes exponentially as it travels through the material. Since the absorbance of a sample is measured as a logarithm, it is directly proportional to the thickness of the sample and to the concentration of the absorbing material in the sample. Some other measures related to absorption, such as transmittance, are measured as a simple ratio so they vary exponentially with thickness and concentration of the material.
| Absorbance | Transmittance | Percent transmittance |
|---|---|---|
| 0 | 1 | 100 |
| 0.1 | 0.79 | 79 |
| 0.25 | 0.56 | 56 |
| 0.5 | 0.32 | 32 |
| 0.75 | 0.18 | 18 |
| 0.9 | 0.13 | 13 |
| 1 | 0.1 | 10 |
| 2 | 0.01 | 1 |
| 3 | 0.001 | 0.1 |
Read more about this topic: Absorbance
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