To explain the basics of how lasers work and let visitors experiment with laser properties.

Transcription

1 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. 3. A 100% reflective mirror. Picture #1 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. Page 1 of 5

2 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. Page 2 of 5

3 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. Page 3 of 5

4 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 Page 4 of 5

5 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: Picture #1 is from Picture #2 is from Page 5 of 5