Download Laser Lights

Laser Lights
Activity Goal
To explain the basics of how lasers work and let visitors experiment with laser properties.
NGSS Domain(s)
PS1.A Structure of Matter
PS3.B Definitions of Energy
PS4.A Wave Properties
PS4.B Electromagnetic Radiation
Related Invention
• Laser
History and Context of Activity (background information for museum staff)
A laser is a device that emits light from the stimulation and amplification of photons (the
elementary particles of light). The first modern laser was created by Theodore Maiman in 1960,
and the word LASER originated as an acronym for Light Amplification by Stimulated Emission of
Radiation.
A laser has a few basic parts:
1. A chamber that holds the laser material, sometimes known as gain medium. This can be
a crystal, gas, liquid, or other substance. The first
laser in 1960 had a ruby crystal as laser material.
2. A light or energy source that pumps energy into
the laser material. This energy stimulates the
electrons within the laser medium to a point that
they give off photons. The photons bounce
around and are amplified within the laser material
and by the mirrors on either end of the chamber.
Picture #1
3. A 100% reflective mirror.
4. A mirror that has a small area where the laser
light can escape.
5. The laser beam.
Because the photons are being excited within a cohesive laser material, most lasers are
monochromatic, meaning that they only have one color or wavelength. Compare this to a regular
light bulb that covers a much wider spectrum of visible light. Also, because most lasers only emit
one color of light, the light is known as being coherent, meaning that they hold together over a
long distance. That’s why you can see laser lights so far away.
Today there are many different types of lasers and many different uses. Many lasers, like the
ones used in this activity, do not produce detectible heat, while others are created specifically to
produce tremendous heat. Some are designed to work within a very specific range of infrared or
ultraviolet light that is invisible to the human eye. Others have very high energy, while others, like
the laser used in this activity, have very low amounts of energy.
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Some of the first commercially available lasers were used in bar code scanners used in grocery
stores, but they are used in nearly countless different ways now, including industrial cutting of
materials such as steel, laser surgery such as LASIK, military guidance systems, CD and DVD
players, and cosmetic uses such as hair removal. Lasers are an integral part of modern
technology.
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Supplies
The only required item for this activity is a laser. Inexpensive red laser pointers (often found on
key chains or similar) will work just fine. High-end powerful green lasers are an unnecessary
expense and could be dangerous.
Safety Notice: NEVER point or shine a laser in anyone’s eye. Even a low powered
laser can potentially cause permanent damage to someone’s retina. It is suggested
that staff supervise use of the laser or maintain control of the laser at all times.
This is an open-ended activity aimed at looking at the properties of laser light, and as such, the
list of possible supplies is nearly endless.
Ideal supplies will be things that you can shine a laser through or reflect off of, such as:
•
Glass or plastic lenses, such as magnifying lenses or reading glasses
•
Clear or colored bottles full of water
•
Crystal cut wine glasses
•
Prisms
•
Mirrors or aluminum foil
•
Polarizing filters from a camera or polarized sunglasses
•
Light gels (colored film used to change the color of things such as spotlights)
•
Incandescent light bulbs, both frosted and clear
•
Ice
•
Fog from a fog machine or from dry ice
Other supplies that may be useful to structure the activity:
•
Cardboard or sheets of poster paper to set up around the laser demonstration area to
keep the laser light from reflecting into the exhibition crowd
•
Adhesive tape
•
A chess board or large grid paper
•
A target
Advance Preparation
Try shining the laser through your various supplies so you can anticipate what effects (if any)
those items will have on the laser beam.
If you wish, set up the cardboard or poster paper around the demonstration area to limit the range
of the laser beam.
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Introducing the Activity (background information for visitors)
Refer to the description and explanation of how a laser works in the History and Context of
Activity section above. A printout of this diagram may be useful in helping to explain how lasers
work.
Picture #2
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Doing the Activity
This activity is about curiosity, making hypotheses, and experimentation. Ask visitors to choose
one or more of the supplies and ask a question or make a prediction, such as, “I wonder what
happens when I shine a laser through a magnifying lens?” or “I think that if I shine a laser at a
mirror that it will reflect back at a right angle.” Let the visitors test their questions and hypothesis
by playing with and manipulating the supplies and the laser.
Note: It is recommended that staff supervise use of lasers at all times. See Safety Notice above.
A more complex (and potentially more fun!) way of experimenting with lasers is to set up a laser
maze. One way to set up a maze is to use a chessboard or other large grid pattern. Designate a
starting point for the laser and create a target that is pointing in an opposing direction. Allow
visitors to place reflective or transparent items only on certain squares on the grid and have them
reflect and direct the laser beam to the target. See who can shine the laser on the target in the
fewest steps or see who can make the most complex maze for the laser to reach the target.
Questions to Ask Visitors
What kinds of machines use lasers? (Examples: DVD players and bar code scanners.)
Do you ever use a laser? What do you use it for? (Example: using a laser pointer to play with
a pet.)
_______________________
This activity is based in part on “Laser Experiments,” available at:
http://www.design-your-homeschool.com/laser-experiments.html
Picture #1 is from http://en.wikipedia.org/wiki/Laser
Picture #2 is from http://www.pcmag.com/encyclopedia_term/0,2542,t=laser&i=45928,00.asp
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