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    Uv Visible Spectros

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    urwah naveed
    UV-visible spectroscopy analyzes electronic transitions in atoms and molecules when electrons move between energy levels upon absorption of ultraviolet or visible light. Compounds that absorb visible light appear colored, while those absorbing only in the UV region are colorless. The instrument contains light sources, a monochromator that splits light into wavelengths, and a detector that compares light intensities passing through a sample and reference to measure absorbance and produce spectra showing absorbed wavelengths. Peaks indicate absorbed colors that are subtracted from visible white light, determining the sample's color.

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    Uv Visible Spectros

    Uploaded by

    urwah naveed
    289 views4 pages
    UV-visible spectroscopy analyzes electronic transitions in atoms and molecules when electrons move between energy levels upon absorption of ultraviolet or visible light. Compounds that absorb visible light appear colored, while those absorbing only in the UV region are colorless. The instrument contains light sources, a monochromator that splits light into wavelengths, and a detector that compares light intensities passing through a sample and reference to measure absorbance and produce spectra showing absorbed wavelengths. Peaks indicate absorbed colors that are subtracted from visible white light, determining the sample's color.

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    UV visible Spectroscopy is a branch of spectroscopy

    Original Title

    Uv Visible Spectroscopy

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    UV-visible spectroscopy analyzes electronic transitions in atoms and molecules when electrons move between energy levels upon absorption of ultraviolet or visible light. Compounds that absorb visible light appear colored, while those absorbing only in the UV region are colorless. The instrument contains light sources, a monochromator that splits light into wavelengths, and a detector that compares light intensities passing through a sample and reference to measure absorbance and produce spectra showing absorbed wavelengths. Peaks indicate absorbed colors that are subtracted from visible white light, determining the sample's color.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    289 views4 pages

    Uv Visible Spectros

    Uploaded by

    urwah naveed
    UV-visible spectroscopy analyzes electronic transitions in atoms and molecules when electrons move between energy levels upon absorption of ultraviolet or visible light. Compounds that absorb visible light appear colored, while those absorbing only in the UV region are colorless. The instrument contains light sources, a monochromator that splits light into wavelengths, and a detector that compares light intensities passing through a sample and reference to measure absorbance and produce spectra showing absorbed wavelengths. Peaks indicate absorbed colors that are subtracted from visible white light, determining the sample's color.

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    © All Rights Reserved
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    of 4

    UV VISIBLE SPECTROSCOPY

    UV Spectroscopytells us about
    electronic transition in atoms and molecules. Spectrum
    are produced when electron and moleculemove from one
    electronic energy level to other of higher energy level.
    COLOURING THE SAMPLE

    Compounds that absorbs in visible region such


    as some Transition Metal compound and Organic Dyes are
    coloured. Those that absorb only in the UV region are
    colorless.

    PROCEDURE
    Inside UV Visible Spectrometer there are usually TWO
    light sources.
    One giving out Visible Light
    And other UV
    (When bulbs give light)
    This one is TUNGSTEN LAMP called HEAD LAMP for the
    Visible region.
    And this one is DEUTRIUM LAMP (for continous spectrum
    in UV region) gives out UV.

    MIRROR:
    This MIRROR directs light from appropriate source into the
    MONOCHROMETER. This contains a Diffraction Grating
    that acts rather like Plain surface of CD to split the light
    into its constitute wavelength.

    Different wavelengths corresponds to different colors.RED


    is about 700nm and BLUE around 350nm. Wavelength
    which are shorter than about 350nm are called ULTRA
    VOLIET.
    Shorter wavelength light has higher energy.
    RADIATION PATH:
    The source produce white light that
    includes all wavelength, colours. The instrument scans
    through the spectrum sending different wavelengths of
    light through the sample in sequence. This is done by the
    Grating which rotates. A single wavelength passes into
    the MODULATORwhich consists of a ROUTER with Mirrors
    on it. This chops the light into beams.
    One beam passes through the Reference Cell, so the
    instrument is reffered as a Double Beam instrument. Both
    sample and the reference beam are directed by mirrors
    on the Detector. This compares their intensities and send
    a Signal proportional to the Ratio of their Intensiities to
    the computer that controls the instrument. The local

    rythem of this ratio gives a quantity called Absorbance.


    Which is a measure of how much light is been absorbed
    by the sample of particular wavelength.
    UV visible spectra are usually
    solutions, light does not normally pass through solid
    samples. Here we will run a spectrum of green food dye.
    To run this spectrum we place some other solvent to the
    sample Cuvette to act as a blank reference. The cuvette
    may be made of glass or plastic, if only the visible region
    spectrum is required. QUARTZcuvette are needed for
    work in UV range because glass and plastics absorb UV
    light.
    We place the sample in second cuvette.
    The blank and the sample are placed in sample holders.
    The lid is closed to prevent light from laboratory
    interfering spectrum. The operator types the detail such
    as wavelength range required andscanning speed into the
    computer that controls instrument. We also 0s the
    instrument at the point where sample doesnt absorb and
    then starts the scan. This spectrum appears on the
    screen. The data is saved on the computer and a
    hardcopy can be printed.
    The horizontal axis is normally wavelength. The
    vertical one is absorbance, which is the measurement of
    the amount of light absorbed by sample.
    The PEAKS on the spectrum are wavelength of
    light that are absorbed by sample and Troughs are where
    light passes through, so the dye absorb ORANGE and

    BLUE light and lets through GREEN so it appears GREEN


    in color.

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