4. spectrometers : Spectrometers are instruments used to identify, measure, and analyze specific wavelengths of substances along a spectrum that is, a group of related data. It breaks light into a spectrum, which is the light's collection of component colors, all of which make up the color of the light as a whole. These spectra are different for every element. This means that by recording the spectra of different elements, one can obtain a reliable method for identifying elements based on the spectra observed. If a certain spectrum is similar to the spectrum of a known element, it can be said that the observed element is that known element.

5. History of spectrometer : The invention of spectrometers and the science of spectroscopy go back to very ancient times. Each invention added more knowledge about the nature of light and mass and its interaction. Sir Isaac Newton invented a simple spectrometer when he used a prism to disperse white light into its constituent colors in the late 1600s. In 1801 British scientist William Wollaston investigated the dark lines in the solar spectrum that suggested the absence of certain spectra of light. German physicist Gustav Kirchhoff was able to show that purified substances display unique light spectra in 1859.

6. Further work by Johann Balmer, Johannes Rydberg, and Niels Bohr was able to detect the energy levels of hydrogen accurately. But it was the work of Werner Heisenberg and Erwin Schrodinger in 1925 that helped to explain the spectra of most elements.

7. Essential components of a spectrometer Slit Collimator Prism or grating Turntable Vernier scale Telescope

8. Slits Slits is a narrow opening through which light enters Collimator It consist of a fixed metallic tube with convex lens at one end and an adjustable slit on other end. When slit is just at the focus of the convex lens the rays of light coming out of the lens become parallel. For this reason it is called collimator. Diffraction Grating It is a glass plate having a large number of close parallel equidistant slits mechanically ruled on it. Prism A prism is a transparent optical element with flat, polished surfaces that refract light. At least two of the flat surfaces must have an angle between them.

9. Turntable A Prism or a grating is placed on a turntable which is capable of rotating about a fixed vertical axis Vernier scale It is a circular scale graduated in half degrees is attached with turn table Telescope It is attached with a vernier scale and is rotatable about the same vertical axis as the turntable

10. Prism spectrometer An instrument composed of a collimator, a prism table, and a telescope is called a prism spectrometer.

11. Operation Light enters through a slit at one end of the collimator and emerges parallel to the axis of the collimator at the other end. The collimated light then strikes a prism that has been appropriately positioned on the spectrometer table. The prism deviates and disperses the collimated light according to Snell’s law and the different wavelengths of light present in the light source. The sets of parallel rays (one set for each wavelength) then enter the telescope and form separate, distinct images of the collimator slit when viewed through the telescope.

12. Grating Spectrometer A grating spectrometer is in every way similar to a prism spectrometer with the exception that a simple, plane diffraction grating replaces the prism as the dispersing element. The function of the collimator and telescope, as well as the general operation of the spectrometer remains unchanged.

13. More Kinds of spectrometer : There are many types of spectrometers, with many possible variations and modifications that can specialize or extend the usefulness of an instrument. Reflection Spectrometers Reflection spectrometers are used to measure the specific wavelengths of light that are reflected by a substance. This is similar to the basis of human vision, which identifies colors using the wavelengths of reflected light. Acoustic Spectrometers Acoustic spectrometers use sound instead of light. They apply pulses of sound to a material and measure how much of particular frequencies of sound pass through the material and how fast different frequencies of sound pass through the material.

14. UV Spectrometers Ultraviolet (UV) spectroscopy works on a principle similar to that of colorimetry, except the light applied to the sample is in the ultraviolet range. UV spectroscopy is also called electronic spectroscopy, because the absorbance characteristics of a sample depends on the configuration of electrons in the chemical bonds of the sample compound. IR Spectrometers Infrared (IR) spectrometers measure the response of a sample when exposed to infrared light. A range of IR wavelengths are passed through the sample to record the absorbance. IR spectroscopy is also called vibrational or rotational spectroscopy because the vibrational and rotational frequencies of atoms bonded to each other, are the same as the frequencies of IR radiation.

15. Atomic Spectrometer Atomic spectrometers are used to analyze the elemental composition of samples and to determine the concentrations of elements of interest. There are two basic types of atomic spectrometers---emission and absorbance. The wavelengths of the emissions or absorbances are characteristic of the elements present. Emission Spectrometers Emission spectrometers work on the principle that when a chemical element is heated by a flame or electric arc it will emit energy. This energy is in the form of light. The spectrometer separates the light into individual frequencies. Because of the quantum nature of light and matter particular elements will only emit light at specific frequencies. Therefore, analysis of the output of a spectrometer allows you to identify particular elements.

16. Absorption Spectrometers Absorption spectrometers are basically the exact opposite of emission spectrometers. Just as heated elements only emit light at specific frequencies, they only absorb light at specific frequencies. Absorption spectrometers work by shining light on a sample of a substance and noting which frequencies are absorbed.

17. Uses Spectrometers are used extensively in astronomy, archaeology and chemical analysis. With the help of prism spectrometer the deviation of light by a glass prism and refractive index can be determined Using diffraction grating the spectrometer can be employed to measure the wavelength of light UV spectrometers are used to study chemical bonding and to determine the concentrations of substances (nucleic acids for example) that do not interact with visible light.. IR spectrometers are used to identify unknown compounds or to confirm their identity since the IR spectrum of a substance is essentially unique. Absorption spectrometers are used in astronomy to determine the atmospheres of distant planets. They are also used in chemistry to find out what elements are present in chemical samples.

18. Acoustic Spectrometers provides information about the various physical properties of the material. If the material is made up of different particles (e.g. sand) acoustic spectrometers can tell you how large the sand grains are.

19. Fields That Use Spectrometers Chemists were the most frequent users of spectrometers and their data, but as refinements and innovations in spectrometers came about, broader uses for the equipment were developed. Today, spectrometers are used to analyze specific types of data in the fields of physics, astronomy, engineering, pharmacology, manufacturing, and medicine.

20. New Uses for Spectrometers Scientists are continually finding new uses for spectroscopy devices to improve our world. Most recent is an instrument called an Inductively Coupled Plasma Mass Spectrometer (ICP- MS), which can detect minute quantities of trace elements, such as uranium in nuclear plant workers' urine --thus helping to safeguard the health and well-being of these workers.

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