When mentioning transmittance we immediately associate this term as the opposite of absorbance. Yet there are certain materials, namely in optics, that is not relevant to make the association. Instead is more important to talk in the ability of such materials to reflect or transmit light, think for example in a lens.

With this concept in mind, we can explain the transmission of light in terms of the second law of Snell, which relates the relation between the angles of reflection and transmission of a material despising the absorbance. Supposing that light is traveling in a matrix of refractive index n1 and is incident on an interface that separates this matrix from another with refractive index n2. When light hits the interface two possible phenomena can occur, the light is reflected or is transmitted.

When light is transmitted we can measure the transparency of a certain material to the incident light, so we can define the transmittance as the ratio between the intensity of transmitted light with the intensity of incident light.

There is a large field in optics where this application is useful, such as measurements of ophthalmic lenses, optical coatings, windows, filters, glass and plastic components. 

When measuring transmittance in liquids the absorbance configurations available from Sarspec are the best option for transmittance measurements. When the purpose is to measure transmittance in solid samples, Sarspec offers a solid sample holder accessory or can configure an holder for a specific configuration.

All the ABSORBANCE SPECK PACKs available from Sarspec are suitable for Transmittance measurements.