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> You can build a diffraction-grating spectroscope:plans
You can build a diffraction-grating spectroscope:plans
ANY SUBSTANCE IN THE KNOWN UNIVERSE CAN BE MADE TO EMIT LIGHT BY HEATING IT TO INCANDESCENCE. THE ATOMS THAT GAVE OFF THE LIGHT CAN BE IDENTIFIED AS THEY PASS THROUGH A SPECTROSCOPE.
SIR ISAAC NEWTON discovered in 1666, that white light is actually a combination of a whole series of colored lights.
THE LIGHT COMING THROUGH A three-cornered prism was not white at all, but consisted of the seven colors of the rainbow. White light is actually a mixture of light waves of different wave lengths, and therefore of different frequencies.
TWO TYPES OF SPECTROSCOPES are in use today. The prism-type which Sir Isaac Newton used, and the newer diffraction grating-type which separates white light into the colors of the spectrum by projecting the light through a transparent material having 13,000 to 14,000 lines per inch on it. Many science students prefer the diffraction grating type because it will show a multitude of Fraunhofer lines (described below).
AS YOU EXPERIMENT with your spectroscope you will notice three different types of spectra: continuous, bright-line, and dark-line or absorptive.
1. CONTINUOUS SPECTRUM An unbroken band of seven colors indicates a continuous spectrum such as produced by incandescent substances, eg. heated Platinum wire.
2. BRIGHT-LINE SPECTRUM Luminous gases or vapors under atmospheric pressure give bright-line spectra. For example, if you turn your spectroscope towards a neon sign, you will see a series of bright vertical lines of various colors on a black background instead of a continuous band of colors.
ELABORATE PROFESSIONALLY-BUILT SPECTROSCOPES are provided with a scale that shows the wave lengths of various lines observed in the spectrum. With your spectroscope, and a wave-length tables found in your chemistry handbook, or library, other unknown substances can be identified.
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