Finding a Green Laser
Setting up the LaserThe laser that I use comes with a couple endcaps that need to be removed or modified before lighting a match. Diffraction Grating - Many lasers come with a cool diffraction grating that transform the beam into hundreds of dancing points of light. While this looks sweet, you can take this filter off. Lens - the second adjustable end cap is a lens that sends the beam in a perfect parallel path to extend the range of the laser. If you unscrew this all the way, it focuses the light beam to a point at around 6-8 cm from the lens. After this point, the beam diverges so the pattern on a distant wall actually looks much wider than it did before Lighting the MatchI have found that the choice of matches matters a lot in making this demonstration successful. Here are the two characteristics that all of the matches have had in common when I've gotten this to work:
Once you have the right match, all you should have to do is aim the laser at the match tip and position it right at the focal point. This point is usually around 6-8 cm but you will have to experiment until you find the sweet spot where the match starts to send off whisps of smoke. ExtensionsHonestly, the laser energy isn't quite as powerful as students are thinking, you can't feel it get hot if you put your hand in the focal point or anything like that but there are still some other things that you can do to demonstrate the energy beyond lighting a match. One of my favorite extensions is to use the laser to light a balloon. You will still need to focus the laser and hold the balloon at the focal length like you did with the match, but there is one additional step that is needed as well. Since you want the laser's energy to be absorbed by the rubber and not enter into the balloon, you will need to make the balloon's surface dark and opaque. I have found that simply coloring a spot on the balloon with a black sharpie usually does the trick. Once that is done, aim the focused laser at the dark spot and hopefully you can get that balloon to pop! :) TroubleshootingSometimes it feels like everything was set up correctly but it doesn't seem to be working... Here are the things that I typically try while troubleshooting this demonstration:
CLICK HERE FOR MORE DEMOSClick for more Waves resources ⬇
Comments
|
Joe CossetteFather, Physics Teacher, Knowles Fellow, Friend, Techie, and Musician Blog Posts |