Absorption, Transmission and Reflection

Infrared energy, when incident upon matter, be it solid, liquid or gas, will exhibit the properties of absorption, reflection, and transmission to varying degrees.

Absorption

Absorption is the degree to which infrared energy is absorbed by a material. Materials such as plastic, ceramic, and textiles are good absorbers. Infrared energy absorbed by real-world objects is generally retransferred to their surroundings by conduction, convection, or radiation.

Transmission

Transmission is the degree to which infrared energy passes through a material. There are few materials that transmit energy efficiently in the infrared region between 7 and 14µm. Germanium is one of the few good transmitters of infrared energy and thus it is used frequently as lens material in infrared cameras.

Reflection

Reflection is the degree to which infrared energy reflects off a material. Polished metals such as aluminum, gold and nickel are very good reflectors.