6.5 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Spectroscopy | 1/5 | https://en.wikipedia.org/wiki/Spectroscopy | reference | science, encyclopedia | 2026-05-05T13:33:39.825730+00:00 | kb-cron |
Spectroscopy is the field of study that measures and interprets electromagnetic spectra as it interacts with matter. In narrower contexts, spectroscopy is the precise study of color as generalized from radiated visible light to all bands of the electromagnetic spectrum. Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of astronomy, chemistry, materials science, and physics, allowing the composition, physical and electronic structure of matter to be investigated at the atomic, molecular and macro scale, and over astronomical distances. Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Current applications of spectroscopy include biomedical spectroscopy in the areas of tissue analysis and medical imaging. Matter waves and acoustic waves can be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO).
== Introduction == Spectroscopy is a branch of science concerned with the spectra of electromagnetic radiation as a function of its wavelength or frequency, as measured by spectrographic equipment and other techniques, in order to obtain information concerning the structure and properties of matter. Spectral measurement devices are referred to as spectrometers, spectrophotometers, spectrographs or spectral analyzers. Most spectroscopic analysis in the laboratory starts with a sample to be analyzed. A light source is sent through a monochromator to spatially separate the colors before passing a selected frequency band through the sample, then the output is captured by a photodiode. For astronomical purposes, the telescope must be equipped with the light dispersion device. There are various versions of this basic setup that may be employed.
Spectroscopy began with Isaac Newton splitting light with a prism; a key moment in the development of modern optics. Therefore, it was originally the study of visible light that we call color. Following the contributions of James Clerk Maxwell, this study later came to include the entire electromagnetic spectrum. Although color is involved in spectroscopy, it is not equivalent to the absorption and reflection of certain electromagnetic waves that give objects or elements a sense of color to our eyes. Rather, spectroscopy involves the splitting of light by a prism, diffraction grating, or similar instrument, to display a particular discrete line pattern called a "spectrum", which is unique for each different type of element or molecule. Most elements are first put into a gaseous state to allow the spectra to be examined, although today other methods can be used for different phases of matter. Each element that is diffracted by a prism-like instrument displays either an absorption spectrum or an emission spectrum depending upon whether the element is being cooled or heated. Until recently all spectroscopy involved the study of line spectra and most spectroscopy still does. Vibrational spectroscopy is the branch of spectroscopy that studies the spectra, which are caused by vibrations of molecules. However, the latest developments in spectroscopy can sometimes dispense with the dispersion technique. In biochemical spectroscopy, information can be gathered about biological tissue by absorption and light scattering techniques. Light scattering spectroscopy is a type of reflectance spectroscopy that determines tissue structures by examining elastic scattering. In such a case, it is the tissue that acts as a diffraction or dispersion mechanism. Spectroscopic studies were central to the development of quantum mechanics. The first useful quantum atomic models, including Bohr model, the Schrödinger equation, and Matrix mechanics, reproduced the spectral lines of hydrogen. These equated discrete quantum jumps of the bound electron in a hydrogen atom to the discrete hydrogen spectrum. Max Planck's explanation of blackbody radiation involved spectroscopy because he was comparing the wavelength of light using a photometer to the temperature of a Black Body. Spectroscopy is used in physical and analytical chemistry because atoms and molecules have unique spectra. As a result, these spectra can be used to detect, identify and quantify information about the atoms and molecules. Spectroscopy is used in astronomy and remote sensing on Earth. Most research telescopes have spectrographs. The measured spectra are used to determine the chemical composition and physical properties of astronomical objects, such as their temperature, elemental abundances, velocity, rotation, magnetic field, and more. An important use for spectroscopy is in biochemistry. Molecular samples may be analyzed for species identification and energy content.
== Theory == The underlying premise of spectroscopy is that light is made of different wavelengths and that each wavelength corresponds to a different frequency. The importance of spectroscopy is centered around the fact that every element in the periodic table has a unique light spectrum described by the frequencies of light it emits or absorbs consistently appearing in the same part of the electromagnetic spectrum when that light is diffracted. This opened up an entire field of study with anything that contains atoms. Spectroscopy is the key to understanding the atomic properties of all matter. As such spectroscopy opened up many new sub-fields of science yet undiscovered. The idea that each atomic element has its unique spectral signature enabled spectroscopy to be used in a broad number of fields each with a specific goal achieved by different spectroscopic procedures. The National Institute of Standards and Technology maintains a public Atomic Spectra Database that is continually updated with precise measurements. With an absorption spectrophotometer, the level of absorption of a light source is determined by the Beer-Lambert Law:
ln
(
I
0
I
)
=
ε
ℓ
c
{\displaystyle \ln \left({\frac {I_{0}}{I}}\right)=\varepsilon \ell c}