AP Night Lecture #1: Waves, Part I

Online Video Lessons:

For animated lessons with narration and problems, visit HippoCampus's AP Physics B II website and scroll down to the "Wave Motion" topics.

Applet Trouble? If you have trouble running the applets below, visit www.java.com to download and install the latest version of Java onto your computer.
  1. Wave definitions
    1. Disturbance propagating through a medium or space which transfers energy
    2. Transverse waves
      1. Displacement perpendicular to wave travel
      2. Up and down look
      3. Light, water
      4. Transverse Waves Java Applet
    3. Longitudinal waves
      1. Displacement parallel to wave travel
      2. Compressions and rarefactions
      3. Sound
      4. Longitudinal Waves Java Applet
  2. Wave reflections
    1. At a boundary, part of a wave is transmitted or absorbed while the rest reflects
    2. If striking more rigid medium, reflection is inverted
    3. If striking less rigid medium, reflection is erect
    4. Wave Reflection & Transmission Applet
  3. Wave terms
    1. Wavelength
      1. Distance between corresponding parts on consecutive waves
      2. Symbol is λ
      3. Measured in meters
    2. Amplitude
      1. Distance from maximum displacement position to equilibrium position
      2. Example is height of a crest or depth of a trough (not both at the same time)
      3. Measured in meters
    3. Frequency
      1. Number of wavelengths passing by a point per second
      2. Measured in 1/s or cycles/s or hertz (Hz)
      3. Inverse is period, which is time for one wavelength to pass a point (in seconds)
    4. Energy - proportional to square of amplitude and square of frequency
    5. Damping - dissipation of wave energy due to friction and other resistive effects
    6. Points in phase or out-of-phase
  4. Wave refraction
    1. Waves bend if the enter a medium at an angle besides 90° and change speeds
    2. Rules of light refraction apply (Snell's Law when we do geometric optics)
  5. Superposition/interference
    1. Wave shapes superimpose (result is the vector sum of the two shapes)
    2. Destructive interference - resulting wave shape is smaller than originals (crest + trough)
    3. Constructive interference - resulting wave shape is larger (crest + crest or trough + trough)
    4. Nodes/antinodes
      1. Pulses of equal but opposite amplitudes and equal wavelengths create motionless node points or lines
      2. Pulses of identical amplitudes and equal wavelengths create antinode points or lines of maximum displacement
    5. Superposition Java Applet
    6. Standing waves
      1. formed when two periodic waves with identical amplitudes and wavelengths travel oppositely and interfere
      2. form stable nodes and antinodes
      3. pipe closed at one end forms resonance lengths of λ/4 for 1st harmonic, 3λ/4 for 2nd, 5λ/4 for 3rd, etc.
      4. pipe open at both ends forms resonance lengths of λ/2 for 1st harmonic, λ for 2nd, 3λ/2 for 3rd, etc.
      5. Harmonics Java Applet
        (Set to Fixed at One end and turn ONLY Fundamental to 100 percent to see CLOSED pipe simulation of 1st harmonic;
         then set ONLY First Overtone to 100 percent to see closed 2nd harmonic;
         then set ONLY Second Overtone to 100 percent to see closed 3rd harmonic, etc.)
        (Set to Free at Both ends and turn ONLY Fundamental to 100 percent to see OPEN pipe simulation of 1st harmonic;
         then set ONLY First Overtone to 100 percent to see open 2nd harmonic, etc.)

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