While often used interchangeably, transmission and transmittance are related but distinct concepts in optics. Transmission refers to the process of light passing through a material, while transmittance is a quantitative measure of the amount of light that successfully passes through a material.
Here's a breakdown:
Transmission:
- Definition: Describes the general act or phenomenon of electromagnetic radiation (like light) passing through a medium. It encompasses all processes involved, including absorption, reflection, and scattering that occur while the light is traveling through the material.
- Nature: Qualitative description; a general observation.
- Example: "The transmission of sunlight through the window glass allows us to see outside." This statement simply describes the light passing through the glass.
Transmittance:
- Definition: A ratio expressing the fraction of incident light (light striking the surface) at a specified wavelength that passes through a sample. It's a measure of how much light actually makes it through.
- Nature: Quantitative measurement, usually expressed as a percentage or a decimal.
- Formula: Transmittance (T) = (Intensity of transmitted light) / (Intensity of incident light)
- Example: "The window glass has a transmittance of 80% for visible light." This means 80% of the light striking the glass passes through.
Here's a table summarizing the key differences:
| Feature | Transmission | Transmittance |
|---|---|---|
| Definition | Process of light passing through a material | Measure of the amount of light that passes through |
| Nature | Qualitative | Quantitative |
| Measurement | No specific measurement | Expressed as a percentage or a decimal |
| Representation | Description of the passage of light | Ratio of transmitted to incident light |
In essence, think of transmission as the event of light going through something, and transmittance as the efficiency of that event. Transmittance is a specific, measurable characteristic that quantifies transmission.
