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Diffraction Grating Kit for 4 slides (Click
here for the Optics page)
Grating width 1.111 nanometer = 900 lines per
millimetre
Base material: 0.05 mm thick acetate
The high line-density of the grating generates
a wide light spectrum similar to that from a prism. If light from
various sources is observed or projected through the transmission
grating it shows, through the spectrum, its special characteristics
and allows the scientist to make important conclusions about the
source of the light.
Instructions
Cut-out the slides, score and fold them. Cut the diffraction film
into 4 equal pieces, and holding them only by the corners, fix them
into the slide window with sticky tape. Glue the two halves of the
slide together. (Take care - Don't get any glue on the diffraction
film.) Observe a light source through the diffraction grating or
project it on to a sheet of white paper.
Light Spectrum and Spectral Analysis
The investigation of the coloured spectrum, formed when light passes
through a Diffraction Grating or Prism, is called Spectral Analysis.
It is one of the most useful investigation methods in Science. Chemists
can detect the smallest amounts of single substances in the spectrum
of the light from a sample, and by using spectral analysis of star-light,
Astronomers can gain important knowledge about the Universe around
us.
Things to do Investigate with your Diffraction
Grating
Sunlight (Take care not to look directly at the sun! You can look
at a bright cloud)
Moonlight - especially in very bright moonlit nights.
Light from Candles or nightlights
Light from different fluorescent tubes and energy saving lamps
Street lights
Neon signs and other illuminated advertisements
The light from particles of chemical salts in a flame (flametest)
The "white" light from a television or computer screen
LEDs - red, green, yellow
Light coming through different coloured filters and liquids with
different chemical substances
Questions to ask yourself when looking at the
Spectra.
Is the Spectrum continuous?
Does it show small lines? What colours? Are some of these double
lines?
Does it show narrow black lines without colour? In which part of
the spectrum?
You can also make a spectroscope with the diffraction
grating and measure the frequency of the spectral lines to an accuracy
of about 5 nanometers.
Web Resources
There are many pages on the web relating to spectroscopy. A search
for "spectroscope" and "diffraction grating"
found the following two sites amongst many others.
http://www.opticsforkids.org/resources/KS_5.pdf
2 page document to make a simple spectroscope.
http://www.sec.noaa.gov/Curric_7-12/Activity_1.pdf
More complex instructions with details on how to calibrate your
instrument
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