is the loss in the power of an electromagnetic radiation that is traveling in a medium. The loss is due to the conversion of light energy to other forms of energy, e.g. lattice vibrations (heat) during the polarization of the molecules of the medium, local vibrations of impurity ions, excitation of electrons from the valence band to the conduction band etc.

Absorption band

is a dark band in the absorption spectrum of a substance, corresponding to a range of wavelengths for which the substance absorbs more strongly than at adjacent wavelengths.

Absorption coefficient

Synonyms :
Attenuation coefficient, Extinction coefficient

characterizes the loss of photons as light propagates along a certain direction in a medium. It is the fractional change in the intensity of light per unit distance along the propagation direction, that is, α=δIIδx. where I is the intensity of the radiation. The absorption coefficient depends on the photon energy or wavelength λ. Absorption coefficient is a material property. Most of the photon absorption 63% occurs over a distance 1/α is called the penetration depth.

Absorption Length

Synonyms :
Attenuation Length

is defined as the distance into a material where the x-ray beam intensity has decreased to a value of 1/e (~ 40%) of the incident beam intensity (Io). Recall that Euler's number e = 2.72.

AC Sensors

can be operated with AC current.                                                                                                                                                                                                                                    

Acceleration Sensors

Acceleration sensors detect vibrations, seismic activities, inclinations in static systems and linear acceleration.