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Put the top on the shoe box. Put rubber bands around the shoe
box to hold the top in place. Hold the shoe box so that the slit is facing
a light source. Make sure that the slit is oriented vertically.
Now look through the diffraction grating into the box.
You should see colors. If you used standard diffraction grating (not rainbow
glasses) you should read the next paragraph. (If not, you can skip it).
If you don't see the spectrum extending to both sides,
the scratches on the grating are not parallel to the slit. Remove the diffraction
grating and rotate it 90 degrees and try again. When the spectrum extends
in both directions from the slit, securely tape the grating in place.
Congratulations, you've successfully created a spectroscope!
Compare the spectra of various lightsources. When you view
different light sources, look for specific colors and notice the spacing
between the colored lines. The heated tungsten filament of an incandescent
light bulb produces a continuous spectrum, where one color shades into another.
The electrically excited mercury vapor in a fluorescent bulb produces distinct
colored lines; the phosphors that coat the inside of the bulb produce a
continuous spectrum.
Some other suggested light sources are a candle flame, the flame from a
Bunsen burner, a flashlight, a Coleman lantern, yellow street lights (sodium
produces the color), blue street lights (mercury vapor produces the color),
neon signs, and slide projector lamps.
Different light sources produce different spectra. You
can see the solar spectrum by looking at sunlight reflecting off a piece
of white paper. DO NOT LOOK DIRECTLY AT THE SUN!
When atoms of different materials are excited by an electric
current or other source of energy, they glow with a unique spectrum. Atoms
of different elements have different colors in their spectra. These characteristic
color patterns represent specific atoms, just as fingerprints serve to identify
different people.
A diffraction grating acts like a prism, spreading light into its component
colors. The light that you see from a light source is the sum of all these
colors. Each color corresponds to a different frequency of light. The diffraction
grating sorts light by frequency, with violet light (the highest frequency
of visible light) at one end of the spectrum and red light (the lowest frequency
of visible light) at the other.
When atoms in a dilute gas (like the mercury vapor in a
mercury street light) radiate light, the light can be seen through a diffraction
grating as a line spectrum, made up of bright lines of color. Each line
in the spectrum of such a gas corresponds to one frequency of light emission,
and is produced by an electron changing energy levels in the atom.
In solids, liquids, and densely packed gases, the situation is not so simple.
As an atom emits light, it collides with other atoms. This changes the frequency
of the light it emits. That's why solids, liquids, and dense gases have
broad bands of light in their spectra.
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