Demonstration of a Principle:
    Standing Waves On Strings, SWIS for short.
         Standing Waves are the Basis of All Stringed and Wind Instruments

Demonstration:

y = sin(x) pronounced "sign"	y = cos(x) pronounced "co-sign"
lo frequency = lo pitch  cello, thunder, train	hi frequency = hi pitch  violin, rain, beeper
hi amplitude = loud  loud music takes more power	lo amplitude = soft  soft music takes less power
node = no motion the hand is the node	antinode = go motion  the bow is the antinode

    Hold arms still in a sine shape, one arm curves up, the other curves down.
    Kind of looks Egyptian doesn't it?

    Do arms in a cosine shape, both arms flap at same time.
    Are you a bird?

    Which is symmetric about the head?
    Do mummies fly?

    The distance from hand to hand is called the WAVELENGTH.
    Flatten arms out, at the flute hand distance, that is quiet.
    Bend arms more, at the flute hand distance, that is loud.
    I want my mummy!

    Now flap the arms in a smooth and perfect wave.
    How often the arms flap, is called the FREQUENCY.
    Spread arms out, that is a cello.
    Bring arms closer, that is a flute.
    A flute makes almost a perfect sine wave.
    Bring them in really tight, that is a violin.

    The idea of FREQUENCY is closely related to the idea of spinning around.
     When the dancer spins SLOWLY, that is a cello wave. (cellist plays low note)
    Spin with the arms in first, MEDIUM , that is a flute wave. (flutist plays middle C)
    Spin with the arms close in    FAST, that is a violin wave. (violinist plays highest note)
    I feel dizzy!

    Both sound AND LIGHT are WAVES
    Spinning SLOWLY is what red light does.  (dancer lit with red spot)
    Spinning MEDIUM is what green light does. (dancer lit with green spot )
    Spinning RAPIDLY is what blue light does. (dancer lit with blue spot)
    And if you fall down that is an X-Ray! (two men appear with a stretcher!)

    The FREQUENCY times WAVELENGTH is the how fast the standing wave would travel if we
    let it go to find ITS mummy.

    Or if you prefer, in unison please:
 

Questions:
    Which takes less power to be heard, a low note or a high note?
    Which travels faster, sound or light?
    Does sound travel faster or slower in water?

Answers:
    Low notes require much more power than high notes.
    Light travels        186,000 miles per second.
    Sound travels  about 1000 feet per second in air, give or take.
    Sound travels nearly 5000 feet per second in water.
 

Reality Checks:
    Beepers and telephones use high notes to get our attention.
    We see the lightning before we hear the thunder.
    Whales can communicate vast distances in the ocean.

Extra Credit
Formula:
    c = f L         - the speed of a wave

Means
    c = speed             - how fast the wave moves away from the source
    f = frequency       - how rapidly the wave vibrates
    L = wavelength     - how long or short the wave is