Scouts-L Mail Archive for February of 1999: Laser pointer demo
Laser pointer demo
Wed, 24 Feb 1999 14:12:42 -0500
On the subject of educating about the dangers of laser pointer: I agree
completely, though I would also support a ban on them if you are under 18.
But, just as I teach my boys to handle guns safely (someone may have a
laser pointer laying around at their house when my sons come over to
visit), likewise an education about laser pointers is an idea that is well
taken. I might have a suggestion for that:
Recently my sons and I went to a Science Museum where one of the shows was
about lasers. It was very interesting. One of the demos could be quite
illuminating (pun not intended). [Note: The instructor used a regular
laser, the pencil lasers may not be strong enough for this demo, so try it
at home before doing it as a demo for a group.] It demonstrated how
lasers could be used for eye (and other) surgery without cutting the outer
layer of the eye.
Here is what he did:
Take 2 balloons, 1 large clear, one smaller black or very dark blue. (You
should be able to get clear balloons at any craft/hobby/florsit shop that
does balloon stuff). Use a blunt pencil to stuff the body of the dark
balloon inside the clear one. Keeping the necks togeher, inflate first the
clear, outer balloon, then the dark, inner balloon. The dark one should be
inflated fully. Tie off the necks.
Shine the laser pointer on the balloon. The inner, darker balloon
explodes, leaving the clear, outer balloon intact. The laser, you see,
heats a hole in the dark material, while the clear material allows the
passage of the light. The outer layer is, of course, the clear portion of
the eye, the dark is the retina, iris, and blood vessels. Very cool and
'gee whiz' stuff. Also very gruesome if you do a "This is your eyeball"
spiel for it.
You might try this, too: try the laser up close, then from across the room
(should be little difference). Then bounce it off of a mirror or
reflective object. What about a comparison? Flashlight, then focus the
beam with a magnifying glass? Have plenty of balloons on hand to show.
(After the first one or two inside the clear ones, it should be suffiecient
to use black balloons, only.)
Kids know that you can burn a leaf or a bug with a magnifying glass. You
would not look into a flashlight 3 inches from your face. A laser, though,
does not lose it's focus or power over 20 feet or more the way a flashlight
Another demo that the instructor did was to shine a laser, then a kid
spritzed a fine spray of water over the path of the beam to show that it
was indeed there, even if we could not see it. Those lasers are just as
dangerous in the daylight as they are in the dark. (good way to show that
the beam is as strong far away as they are up close).
If anyone has a laser that they can try the balloon demo above, please let
the rest of the list know if it works. I think a visual will say more than
Sorry this is so long,