3. 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.
4. 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.
5. • 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.
6. Essential components of a
spectrometer
Slit
Collimator
Prism or grating
Turntable
Vernier scale
Telescope
7. 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.
8. 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. Operation
•Light enters through a
slit at one end of the
collimator and emerges
parallel to the axis of the
collimator at the other •The prism
end. The collimated light deviates and disperses the
then strikes a prism that collimated light according to
has been appropriately Snell’s law and the
positioned on the different wavelengths of light
spectrometer table. 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.
11. 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.
12. 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.
13. 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.
14. 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.
15. 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.
16. 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.
17. • 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.
18. 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.
19. 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.
