30. Introducing the Laser

The laser is used in many demonstrations, but the students are delighted with the device itself.

First make a spot on the side wall and then catch it on your hand to show that the beam will not burn a hole through your hand. A short discussion of the dangers of looking down the beam is appropriate at this point.

Then place the laser on the table so the beam hits the side wall, walk along to the middle of the beam, and clap erasers over it so the pencil-like beam is outlined in falling chalk dust. We also have fog-in-a-can available for outlining the laser beam. (This is very effective.)

A similar stunning demonstration for a small group to gather around is to ask for a volunteer with a diamond ring. Beam the laser into the diamond, and clap chalk dust over it. The many tiny beams emerging from the diamond are very beautiful. The beam pattern can be used to "fingerprint" the diamond uniquely.
Another short demonstration is to place a human hair in the beam. From the resulting diffraction pattern and the wavelength of the laser, you can calculate the diameter of the hair.

A Metrologic publication "101 Ways to Use a Laser" is available.