Discuss the process of the absorption of light by matter in terms of the atomic structure of the absorbing medium.

Atoms consist of a nucleus made up of protons and neutrons surrounded by electrons that occupy specific energy levels or orbitals. In a solid or liquid medium, these atoms or molecules are arranged in a specific pattern, forming a lattice. The electrons surrounding the nucleus are responsible for absorbing or emitting photons when they transition between energy levels.

When light (electromagnetic radiation) interacts with matter, its photons can be absorbed by the electrons in the atoms. This occurs when the energy of the incoming photon matches the energy difference between two energy levels in the atom. The electron then gets excited to a higher energy level, and the photon ceases to exist.

When an electron absorbs a photon, it gets excited and jumps to a higher energy level. This transition of electrons from a lower to a higher energy level is called excitation. The energy difference between these two energy levels is equal to the energy of the absorbed photon, which can be expressed mathematically as: \[E = h \nu\] where \(E\) is the energy of the photon, \(h\) is the Planck's constant, and \(\nu\) is the frequency of the light.

After excitation, the electron stays in the excited state for a short time (nanoseconds to microseconds). Eventually, the electron will return to its original energy level, a process known as relaxation. During relaxation, the energy that was absorbed by the electron is released, often in the form of another photon with the same energy as the absorbed one. This emitted photon can be in the visible, infrared, or ultraviolet range depending on the energy difference between the energy levels.

The absorption of light by matter results in an absorption spectrum, which is a graphical representation of the absorption of light at different wavelengths or frequencies by a substance. It shows the specific wavelengths of light that are absorbed by the substance, leading to transitions of electrons between specific energy levels. This spectrum is unique to each substance and can be used to identify the matter and determine its concentration. To summarize, the absorption of light by matter involves the interaction of photons with the electrons in the atomic structure of the absorbing medium. The absorption of a photon leads to the excitation of an electron to a higher energy level, which then eventually returns to its original level through relaxation, emitting a photon with the same energy. The resulting absorption spectrum is unique to the substance, allowing for its identification and analysis.