Lissajous figure demo

[Leigh Palmer <palmer@SFU.CA>]

> 103.  Rig two electric motors on a stand.  Motor shafts are attached to
> vertical mirrors that get spun.  Mirrors are set up so that a laser bounces
> from one mirror to the other mirror and then onto a screen.   When one motor
> spins, laser forms a circle on the screen.  By spinning second motor at
> different speeds and changing its direction, can form all sorts of intricate
> patterns.

I do this with two tuning forks fitted with mirrors made from
aluminized microscope cover slips. I fit the forks into lead
bricks to hold them solidly and position them in the laser beam
with lab jacks*. Works in a large lecture room, and the forks
can be made audible with a microphone and amplifier (I use my
wireless mic). The Lissajous figures can be shown to be related
to consonances between the forks. Works beautifully!

Leigh

*They oscillate in mutually perpendicular planes.