Spectrometer

A spectrometer is an optical instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization state. The independent variable is usually the wavelength of the light, normally expressed as some fraction of a meter, but sometimes expressed as some unit directly proportional to the photon energy, such as wavenumber or electron volts, which has a reciprocal relationship to wavelength. A spectrometer is used in spectroscopy for producing spectral lines and measuring their wavelengths and intensities. Spectrometer is a term that is applied to instruments that operate over a very wide range of wavelengths, from gamma rays and X-rays into the far infrared. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... See also list of optical topics. ... This article does not cite any references or sources. ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... Spectroscopy is the study of spectra, ie. ... In physics, intensity is a measure of the time-averaged energy flux. ... In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... The wavelength is the distance between repeating units of a wave pattern. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... Wavenumber in most physical sciences is a wave property inversely related to wavelength, having SI units of reciprocal meters (m−1). ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ... Extremely high resolution spectrogram of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of the interaction between radiation (electromagnetic radiation, or light, as well as particle radiation) and matter. ... A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ... The wavelength is the distance between repeating units of a wave pattern. ... This article is about electromagnetic radiation. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ...

In general, any particular instrument will operate over a small portion of this total range because of the different techniques used to measure different portions of the spectrum. Below optical frequencies (that is, at microwave, radio, and audio frequencies), the spectrum analyzer is a closely related electronic device. This article is about the type of Electromagnetic radiation. ... Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... A spectrum analyzer is a device used to examine the spectral composition of some electrical, acoustic, or optical waveform. ...

Spectroscopes

Spectrometers

They are used often in astronomy and some branches of chemistry. Early spectroscopes were simply a prism with graduations marking wavelengths of light. Modern spectroscopes, such as monochromators, generally use a diffraction grating, a movable slit, and some kind of photodetector, all automated and controlled by a computer. The spectroscope was invented by both Gustav Robert Georg Kirchhoff and Robert Wilhelm Bunsen. For other uses, see Astronomy (disambiguation). ... For other uses, see Chemistry (disambiguation). ... Diagram of a triangular prism, dispersing light Lamps as seen through a prism. ... A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light chosen from a wider range of wavelengths available at the input. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Photosensors or photodetectors appear in several varieties: Photoresistors or Light Dependant Resistors (LDR) which change resistance when illuminated Photovoltaic cells or solar cells which produce a voltage and supply an electric current when illuminated Photodiodes which can operate in photovoltaic mode or photoconductive mode Phototubes containing a photocathode which emits... This article is about the machine. ... Gustav Robert Kirchhoff (March 12, 1824 - October 17, 1887), a German physicist who contributed to the fundamental understanding of electrical circuits, spectroscopy, and the emission of black-body radiation by heated objects. ... Robert Wilhelm Bunsen (31st March, 1811 – 16th August, 1899) was a German chemist. ...

When a material is heated to incandescence it emits light that is characteristic of the atomic makeup of the material. Particular light frequencies give rise to sharply defined bands on the scale which can be thought of as fingerprints. For example, the element sodium has a very characteristic double yellow band known as the Sodium D-lines at 588.9950 and 589.5924 nanometers, the colour of which will be familiar to anyone who has seen a low pressure sodium vapor lamp. Molten glassy material glows orange with incandescence in a vitrification experiment. ... This article does not cite any references or sources. ... For sodium in the diet, see Edible salt. ... A LPS / SOX streetlight at full power A sodium vapor lamp is a gas discharge lamp which uses sodium in an excited state to produce light. ...

In the original spectroscope design in the early 19th century, light entered a slit and a collimating lens transformed the light into a thin beam of parallel rays. The light was then passed through a prism (in hand-held spectroscopes, usually an Amici prism) that refracted the beam into a spectrum because different wavelengths were refracted different amounts due to dispersion. This image was then viewed through a tube with a scale that was transposed upon the spectral image, enabling its direct measurement. A collimating lens is a lens used to gather together a parallel beam of light. ... An Amici prism, named for the astronomer Giovanni Amici, is a type of compound dispersive prism which is used as a spectrometer. ... The straw seems to be broken, due to refraction of light as it emerges into the air. ... Dispersion of a light beam in a prism. ...

With the development of photographic film, the more accurate spectrograph was created. It was based on the same principle as the spectroscope, but it had a camera in place of the viewing tube. In recent years the electronic circuits built around the photomultiplier tube have replaced the camera, allowing real-time spectrographic analysis with far greater accuracy. Arrays of photosensors are also used in place of film in spectrographic systems. Such spectral analysis, or spectroscopy, has become an important scientific tool for analyzing the composition of unknown material and for studying astronomical phenomena and testing astronomical theories.The wavelengths are measured with the spectrometer. This article or section does not cite its references or sources. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ...

Comparison of different diffraction based spectrometers: Reflection optics, refraction optics, fiber optics

Image File history File links Download high resolution version (403x663, 29 KB) Summary Licensing File links The following pages link to this file: Spectrometer ... Image File history File links Download high resolution version (403x663, 29 KB) Summary Licensing File links The following pages link to this file: Spectrometer ...

Spectrographs

A spectrograph is an instrument that transforms an incoming time-domain waveform into a frequency spectrum, or generally a sequence of such spectra. There are several kinds of machines referred to as spectrographs, depending on the precise nature of the waves.The first spectrographs used photographic paper as the detector. The star spectral classification and discovery of the main sequence, Hubble's law and the Hubble sequence were all made with spectrographs that used photographic paper. The plant pigment phytochrome was discovered using a spectrograph that used living plants as the detector.More recent spectrographs use electronic detectors, such as CCDs which can be used for both visible and UV light. The exact choice of detector depends on the wavelengths of light to be recorded. Waveform quite literally means the shape and form of a signal, such as a wave moving across the surface of water, or the vibration of a plucked string. ... Familiar concepts associated with a frequency are colors, musical notes, radio/TV channels, and even the regular rotation of the earth. ... Until the advent of digital photographic processes, the sole meaning of Photographic Paper was paper coated with light-sensitive chemicals. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... Hubbles law is the statement in physical cosmology that the redshift in light coming from distant galaxies is proportional to their distance. ... Astronomers classify galaxies based on their overall shape (elliptical, spiral or barred spiral) and further by the specific properties of the individual galaxy (for example degree of ellipse, number of spirals or definition of bar). ... Phytochrome is a photoreceptor, a pigment that plants use to detect light. ... A specially developed CCD used for ultraviolet imaging in a wire bonded package. ... For other uses, see Ultraviolet (disambiguation). ...

The forthcoming James Webb Space Telescope will contain both a near-infrared spectrograph (NIRSpec) and a mid-infrared spectrometer (MIRI). The James Webb Space Telescope (JWST) is a planned space infrared observatory, intended to be a significant improvement on the aging Hubble Space Telescope. ...

An Echelle Spectrograph uses two diffraction gratings, rotated 90 degrees with respect to each other and placed close to one another. Therefore an entrance point and not a slit is used and a 2d CCD-chip records the spectrum. Usually one would guess to retrieve a spectrum on the diagonal, but when both grating have a wide spacing and one is blazed so that only the first order is visible and the other is blazed that a lot of higher orders are visible, one gets a very fine spectrum nicely folded onto a small common CCD-chip. The small chip also means that the collimating optics need not to be optimized for coma or astigmatism, but the spherical aberration can be set to zero. To meet Wikipedias quality standards, this article or section may require cleanup. ... Focal plane Longitudinal sections In optics, spherical aberration is an image imperfection that occurs due to the increased refraction of light rays that occurs when rays strike a lens or mirror near its edge, in comparison with those that strike nearer the center. ...

A spectrograph is sometimes called polychromator, as an analogy to monochromator. A polychromator is an optical device. ... A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light chosen from a wider range of wavelengths available at the input. ...

Acoustic uses

acoustic spectrogram of the spoken Japanese word minato

In acoustics, a spectrograph converts a sound wave into a sound spectrogram. The first acoustic spectrograph was developed during World War II at Bell Telephone Laboratories, and was widely used in speech science, acoustic phonetics and audiology research, before eventually being superseded by digital signal processing techniques. Image File history File links Download high resolution version (1800x1125, 131 KB) Spectrogram [minato].png info spectrograph of the Tokyo Japanese word [minato] generated with Praat from an . ... Image File history File links Download high resolution version (1800x1125, 131 KB) Spectrogram [minato].png info spectrograph of the Tokyo Japanese word [minato] generated with Praat from an . ... It has been suggested that this article or section be merged with periodogram. ... Minato (港) is Japanese for port. ... Acoustics is a branch of physics and is the study of sound (mechanical waves in gases, liquids, and solids). ... This article is about compression waves. ... It has been suggested that this article or section be merged with periodogram. ... Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ... Acoustic phonetics is a subfield of phonetics which deals with acoustic aspects of speech sounds. ... Audiology is the branch of science that studies hearing, balance, and their disorders. ... Digital signal processing (DSP) is the study of signals in a digital representation and the processing methods of these signals. ...

Reference works

• J. F. James and R. S. Sternberg, The Design of Optical Spectrometers (Chapman and Hall Ltd, 1969)
• John James, Spectrograph Design Fundamentals (Cambridge University Press, 2007) [ISBN 0521864631]
• How to work with the spectroscope : a manual of practical manipulation with spectroscopes of all kinds

1882; Browning, John (1835-1925) NOT_IN_COPYRIGHT - online full-text download

See also

• List of light sources
• Photometry (optics) Main Photometry/Radiometry article - explains technical terms
• Spectroscopy
• Mass spectrometer
• By Anna Srinivas

A Standard Household Light bulb This page is a list of sources of light. ... Photopic (black) and scotopic [1] (green) luminosity functions. ... Extremely high resolution spectrogram of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of the interaction between radiation (electromagnetic radiation, or light, as well as particle radiation) and matter. ... Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ...

External links

• The Optics of Spectroscopy Tutorial
• How to design a spectroscope
• A CD spectrometer Build from CD and cereal box - Spectrographs of common light sources
• Supplement: Build Yourself a Simple Hand-Held Spectrograph Sample spectra
• SPECTROSCOPY FOR THE SCHOOL Build a simple spectroscope from a CD
• CD spectrometer CD + cardboard tube or cereal box
• [1] Construction photos, razor-blade slit
• MiniSpectroscopy displays a visual representation (a "spectroscope view") of a sample spectrum simultaneously with a graphical (intensity vs. wavelength) representation.