Absorption is the absorption of waves or frequencies. This effect occurs equally in optical and electrical transmission media and quadrupoles, but also in radio technology and acoustics. In general, all absorption involves the energy of electromagnetic waves, light waves, or sound waves being absorbed by the medium.
In absorption, part of the energy is absorbed, another part is reflected and thus subject to reflection, and another part can be transmitted by the medium, this energy is subject to transmission. The ratio between the absorbed energy and the energy available in front of the medium is called the absorption coefficient or absorption coefficient. The absorption coefficient can take values between 1 and 0. It is then 1 when the complete incident energy is absorbed and 0 when no incident energy is absorbed.
- In radio technology, absorption involves the electromagnetic energy being absorbed by buildings, topological elevations, and also moisture particles in the air, and converted into heat. This phenomenon is very pronounced in microwave technology and increases rapidly with higher frequencies and as a function of relative humidity. In rain, the absorption of microwaves is much higher than in fog. In rain, it can assume attenuation values of 0.001 dB/km at frequencies of 1 gigahertz( GHz), which can increase to 10 dB/km or more at 5 GHz.
- In optical transmission technology, absorption is about the light that has been fed into an optical waveguide and the light that it has absorbed. Molecular structures in the glass are responsible for this energy extraction that takes place in the optical waveguide. The absorption in an optical waveguide is mainly due to two factors, namely the molecular structure of the base material and possible impurities in the fiber core. Due to the molecular structure of the optical waveguide, resonances occur which cause higher attenuation by absorption at corresponding frequencies. The result is pronounced resonance points that are used as optical windows for transmission purposes.
- In lighting and color technology, absorption is the conversion of electromagnetic radiation energy into another form of energy such as heat. Certain colors absorb light, while others reflect it.
- In acoustics, absorption is when soft material or material with a porous surface picks up sound pressure and absorbs it in the form of deformation or movement. Acoustic absorption is frequency dependent. The value for absorption is the absorption coefficient. It is expressed in 'alpha' and can take the values between 'alpha' equal to 0 for total reflection and 'alpha' equal to 1 for total absorption. The devices for acoustic absorption are called absorbers. In addition to the absorbers that are strongly frequency dependent, there are materials with which broadband absorption can be achieved, such as porous plates, curtains, carpets, glass wool and rock wool. They are very efficient when the air movement is the fastest, i.e. the sound vel ocity is the greatest.