12/15/09

Post date: Dec 15, 2009 2:18:50 PM

Bell Ringer: Why does the laser (reflecting off a speaker) bounce around so much?

• • Sound as vibration

    • Speaker vibrates, causes air molecules to vibrate

    • Vibration of speaker causes vibration of laser (reflecting off a vibrating mirror)

  • Sound as a pressure wave

    • As speaker moves forward and backward, it compresses and expands the air

    • Compressions and expansions (rarefactions) move outward from the source

    • Ear is a very sensitive pressure sensor (can detect pressure change when going in an airplane, driving up or down a big hill, or even changes in the weather)

    • Ruben's Tube demonstration - flame height indicates amount of pressure

  • Finish 16.1 Notes

• 16.1 Review due tomorrow