Can the phenomenon of beats be observed with light?
Yes. Adjacent modes in a laser will beat against one another, producing a
detectable signal somewhere in the UHF television band. This can be
"observed" via photodetector and amplifier circuit fed into television
antenna leads.
Since there are typically more than two modes active simultaneously, there
is also a "beat between beats" phenomenon which can also be detected. This
one is in the acoustic frequency range, and you can amplify the signal and
listen via a loudspeaker.
Reference for much more detail - the above is from memory:
George Spagna **********************************************
Department of Physics * *
Randolph-Macon College * "It requires a very unusual mind *
P.O. Box 5005 * to undertake the analysis *
Ashland, VA 23005-5505 * of the obvious." *
* *
phone: (804) 752-7344 * - Alfred North Whitehead *
FAX: (804) 752-4724 * *
e-mail: gspagna@rmc.edu **********************************************
URL: www.rmc.edu/~gspagna/gspagna.html