Energiabsorption

Energiabsorption refers to the process by which a material or system takes in energy from an external source and converts it into other forms, such as heat, electronic excitation, or mechanical motion. It is a central concept in optics, acoustics, thermodynamics, and materials science, and it is used to describe how much of an incoming energy flux is removed from a beam, wave, or field as it passes through a medium. Absorption is typically described by coefficients or fractions that depend on frequency or wavelength and geometry.

In electromagnetic contexts, photons may be absorbed when they match electronic, vibrational, or lattice transitions in a material. The Beer-Lambert law relates incident and transmitted intensity by I = I0 e^{-αx}, where α is the absorption coefficient and x is path length. The absorptance or absorbance (A) is a dimensionless quantity often given by A = -log10(I/I0). Materials exhibit wavelength-dependent spectra that reveal electronic structure and bonding.

In acoustics, energy absorption at a surface is quantified by the absorption coefficient, ranging from 0 (total reflection) to 1 (complete absorption). Materials such as porous foams or fibrous sheets convert sound energy to heat through viscous losses and friction, reducing reverberation.

Other contexts include thermal energy absorption (specific heat and heat capacity determine how much energy is needed to raise temperature), and applications in solar energy, photodetection, radiative shielding, or thermal insulation.

Measurement and units: optical spectroscopy uses spectrophotometry; calorimetry measures absorbed heat; acoustics uses impedance and absorption coefficients.