Ok, here's a rather lengthy Q

Who can explain beat frequencies, harmonics and all that jazz? [/B][/QUOTE]

Not lengthy. Okay, beat frequencies are simple. The beat frequency is the difference between two frequencies, ie, 240 Hz and 242 Hz means beat frequency is 2 Hz. Not so tough. It's just periodic loudness variation when two similar pitches are sounded simultaneously. I could do the wave derivation, but it's much easier to just think of it this way. Think of it this way- if you have a tuning fork and clamp it, you decrease the frequency- it goes flat. Why? Because of angular acceleration. The tines are trying to vibrate but you just increased their moment of inertia, so they are now dissonant with another tuning fork of the same original frequency. That dissonance you hear is beating.

Harmonics:

initial frequency, with ONE node is referred to as the "fundamental frequency" also known as the first harmonic.

Simple: When you have an open pipe (antinode-antinode) or you're in the middle of a closed pipe (node-node) then ALL harmonics are allowed. To find the new frequency of the harmonic, just multiply the fundamental frequency by its integer (ie 2nd harmonic = 2 x fundamental frequency). For Node-Antinode conditions, only ODD harmonics are allowed because of boundary conditions. So you multiply by 1, 3, 5, 7 etc.

I can't explain Jazz. Sorry.

Okay, here's one:

If you are farsighted then your _____ point is too ______. You fix with a _________ lens.

If you are nearsighted, your ________point is too _______, and you fix it with a ________ lens.

Bonus: What is the sign of the power of the lens you use to fix each problem, respectively?