The electromagnetic spectrum is made up of certain
waves. These waves are actually quite common to us.
For example, radio waves usually come from radios,
infrared radiation (IR) waves can come from a remote
control, ultraviolet waves can come from the sun, and
X-ray and gamma rays waves can come from
radioactive material. These waves are not seeable to
our eyes. Visible light is the most commonly seen
region of waves. Visible light waves can be thought of
as the seven colors of a rainbow. Each of the colors has
a different wavelength. On one end, there is red which
has a long wavelength, and the other, violet with a
short wavelength. When we see light of a certain color,
it means we are seeing certain wavelengths. However,
certain visible light wavelengths of light are still nonseeable. These wavelengths can be seen with the help
of instruments. A spectroscope can help us see the
different wavelengths of light from certain light
sources. A diffraction grating makes this possible. A
diffraction grating takes a light source and separates
the wavelengths. The way it works is light will make
contact with a grating, like the figure seen below, then
depending on the number of lines and the spacing of
each line, wavelengths of light can be separated, or
diffracted. Surprising as it might be, a CD disc also has
lines that can be used as a grating. This experiment will
utilize the lines of a CD and diffract light of a light
source to see the different wavelengths not seen to the
visible eye.
Rainbows are an example of when certain
wavelengths of light can be seen by anyone. Many
colors can be seen by the visible eye. In the case of
rainbows, sunlight will travel through the air until it
makes contact water like from rain. This will then
cause light to bend. The bend of sunlight will
determine the which colors can be seen. The degree
of much bend there is will determine the wavelength
or color is seen. That is why during or after it rains,
once sunlight appears, light is bend creating the colors
from red to purple.
It is fairly common to see a neon light sign that says
“OPEN” or a logo of a certain brand be lit up in
various colors. The neon colored light coming from
the tube is actually filled with a certain gas. For a
certain color of neon light, a specific type of gas must
be used. For example, to get a light blue light, helium
would be filled into a tube.
https://www.youtube.com/watch?v=fl42pnUbCCA
http://www.cnrt.scsu.edu/courses/psc150/nova_c
ourse_website/07_Wave_Motion/EM_Spectrum/Vi
sible_Light.html
https://www.youtube.com/watch?v=F6dZjuw1KUo
https://www.youtube.com/watch?v=7CmbItRjM-Y
https://imagine.gsfc.nasa.gov/science/toolbox/ems
pectrum1.html
Pamphlet written by Orvik Lozano. For more information,
contact Prof. Michael Grubb at 970-247-7238.
Have you ever wondered what makes lit up signs
like “OPEN” signs appear in colorful, neon-like
colors? These colors come from certain gases of a
specific element. Helium, for example, can be seen
as a light bluish color. However, does that mean
only one wavelength of light is being seen? That is
not the case. Even though our eyes only see the
light blue color, there are several wavelengths of
light that can be seen. In other words, certain other
colors can be seen, just not with our eyes. To be
able to see these non-seeable colors, a
spectroscope will be need. A home-made CD
spectrometer is a cost-effective instrument that will
allow us to see multiple wavelengths of light. This
means that a light source passing through the slit
will be reflected off the CD and then bend light
enough so that it can be visibly to show
wavelengths of light that are unique to certain light
sources. Why use a CD and not a DVD or Blu-ray?
Using a DVD and Blu-ray would indeed increase the
resolution by separating even more wavelengths of
light. This, however, would require a more complex
setup since the groove spacing of a DVD and Blu-ray
are much different than that of a CD. The purpose
of using a CD makes for a cheap and easy method
to see wavelengths of light from a source of light.
Helium
Lamp
Helium spectrum through
a CD spectroscope
Step #1: The
materials of a
black foam-core
board, a blank CD
disk, two straightedge blades,
electrical tape,
scotch or duck
tape, and scissors
will be used.
Step #5: Take
scotch or duck
tape and place
pieces of tape
all over the
metal foil.
Step #2: The foam
is cut into four 23”X 10-12” pieces.
Tape the four
pieces to make a
hollow tube. Make
certain no light
gets through the
gaps of each piece.
Step #3: Take the two
straight-edge blades
and tape them together
to create a narrow slit
on one end of the tube.
The slit must be as
narrow and parallel of
each other as possible.
Step #4: Take the
blank CD and
scratch a little of
the metal foil off
the edge of the
CD using a blade.
Step #6: If small chunks of metal foil are still present,
use tape to remove the remaining pieces.
Step #7: Cut a piece
about a fourth of the
CD. Be sure not to
dirty the side were the
metal foil one was,
Step #8: Tape the CD
piece to the tube.
The side were the
metal foil once was
should face the
inside of the tube.
Wavelengths of light
should now be
seeable through it.