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For more information, please see full course syllabus of AP Physics B
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  • Principle of linear superposition: When two or more waves are present in a certain place, the disturbance at each point is the sum of the disturbances of each wave.
  • Interference: if two waves arrive at a point in phase they will interfere constructively; the intensity at that point will be enhanced. Destructive interference results if the phase difference is 180 degrees.
  • When a wave goes through a slit, it bends around the edges; a central maximum is obtained, followed by a succession of dark and bright bands.


Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Principle of Linear Superposition 0:10
    • Example: String Sending Two Pulses
    • Sum of Two Pulses
  • Interference 11:56
    • Two Speakers Driven By Same Frequency
    • Constructive Interference
    • Destructive Interference
  • Example 37:25
    • Two Speakers
    • Speed of Sound
  • Diffraction 43:53
    • Circular Aperture
  • Beats 52:15
    • Two Frequency
    • Time Separated by 1 sec
  • Extra Example 1: Two Speakers
  • Extra Example 2: Tube and Sound Detector