12/2/09

Post date: Dec 01, 2009 8:20:37 PM

Bell Ringer: Imagine you are floating on a boat near a dock. You have a stopwatch and a meter stick with you. How would you calculate the speed of the waves as they go by you?

• Wave speed lab

  • Calculating the speed of waves on a spring. Due Thursday.

  • Wave speed

    • Depends on what type of wave

      • Sound waves move faster than water waves

    • Depends on properties of the medium

      • molecules that are closer together transmit waves faster

      • Gases - farthest apart, so slowest waves

      • Liquids - closer together, so faster waves

      • Solids - closest together, so fastest waves (try tapping on desk with ear pressed to it... do you hear it better with your ear to the table or the one that's not on the table?)

    • Light has definite speed = 300,000,000 m/s in a vaccuum.

  • Doppler effect

    • Waves move at a certain speed, regardless of how fast the wave source is moving

      • Waves ahead of source get squeezed together for a higher pitch, waves behind get spread apart for lower pitch

    • Page 522 for picture and explanation

    • Frequency changes when the object making a wave is moving

    • Example

      • Sound waves

        • chime moving forward and backward

        • plastic tubes

      • Light waves

        • red shift

• 15.2 Review (pg. 523: 1-9) due Thursday