When an atom absorbs light or waves, a process called absorption occurs. Absorption happens when an atom or molecule gains energy from an incoming photon, resulting in the excitation of an electron within the atom or molecule to a higher energy level. The general steps involved in this process are as follows:
Incident Light: Light, which can be described as electromagnetic waves, carries energy in discrete packets called photons. These photons can have different wavelengths or energies, corresponding to different regions of the electromagnetic spectrum such as visible light, ultraviolet light, or infrared light.
Energy Matching: For an atom to absorb a photon, the energy of the photon must match the energy difference between the initial and final energy levels of an electron within the atom. The energy levels of electrons in atoms are quantized, meaning they can only occupy specific energy states.
Absorption: When a photon with the appropriate energy encounters an atom, it interacts with an electron in the atom. The energy of the photon is transferred to the electron, causing it to transition from its lower energy state (ground state) to a higher energy state (excited state). This absorption process is nearly instantaneous.
Excited State: In the excited state, the electron is in a higher energy level than its original position. This higher energy level is unstable, and the electron tends to return to its original state.
Emission or Relaxation: The excited electron can return to its original state through different processes. It can emit a photon of energy equal to the energy difference between the excited and ground states. This emitted photon may have the same wavelength or energy as the absorbed photon, resulting in the phenomenon of fluorescence or phosphorescence. Alternatively, the energy can be dissipated through non-radiative processes, where the energy is transformed into other forms like heat.
It's important to note that the absorption of light or waves is specific to the energy levels of the atom or molecule involved. Each atom has a unique set of energy levels, and therefore, it absorbs and emits light at specific wavelengths or energies, giving rise to the characteristic absorption and emission spectra observed in spectroscopy. This principle is fundamental to various fields of science, such as chemistry, physics, and astronomy, where the study of light absorption plays a crucial role in understanding the behavior of matter and the composition of substances.