Sign In | Subscribe

Enter your Sign on user name and password.

Forgot password?
  • Follow us on:
Start learning today, and be successful in your academic & professional career. Start Today!
Loading video...
This is a quick preview of the lesson. For full access, please Log In or Sign up.
For more information, please see full course syllabus of AP Physics B
  • Discussion

  • Study Guides

  • Download Lecture Slides

  • Table of Contents

  • Related Books & Services

Start Learning Now

Our free lessons will get you started (Adobe Flash® required).
Get immediate access to our entire library.

Sign up for

Membership Overview

  • Unlimited access to our entire library of courses.
  • Search and jump to exactly what you want to learn.
  • *Ask questions and get answers from the community and our teachers!
  • Practice questions with step-by-step solutions.
  • Download lesson files for programming and software training practice.
  • Track your course viewing progress.
  • Download lecture slides for taking notes.
  • Learn at your own pace... anytime, anywhere!


  • Diffraction is the bending of waves around obstacles.
  • Huygen’s Principle: Every point on a wave front acts as a source of wavelets that move forward at the wave speed; the wave front at a latter time is the surface tangent to the wavelets.
  • Diffraction of light from a narrow slit: If the screen is far away, the first dark fringe occurs for an angle theta given by

    Sin (theta) = lambda / W

    where lambda is the wavelength of light, W is the width of the slit, and theta is the angle that the line from the center of the slit to the dark fringe makes with the line from the center of the slit to the central maximum.

  • In general dark fringes occur at angles theta given by

    Sin(theta) = m * lambda / W

    where m = 1, 2, 3,… The bright fringes are situated halfway between the dark ones.


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
  • Diffraction of Waves 0:18
    • Source of Sound Waves
    • Huygens' Principle
  • Diffraction of Light from Narrow Slit 10:57
    • Light From a Distant Source
    • Pick Any Point
    • Source of Wave Front
    • Waves Traveling Parallel to Each Other
    • Franhofer Diffraction
    • Drawing Perpendicular
    • First Maximum
    • Every Wave Has Interference and Diffraction
  • Width of Central Maximum 32:49
    • Width of Slit is 0.2 mm
    • Monochromatic Light
    • If Angle is << 1
    • If W= 2cms
  • Intensity of Diffraction Patterns 44:21
    • Plotting Intensity Versus Light
  • Resolution 45:35
    • Considering Two Source
    • Two Objects Resolved
    • Rayleigh Principle
  • Diffraction Grating 51:18
    • First Order Max
    • Intensity Shown in Figure
  • Extra Example 1: Slit Diffraction
  • Extra Example 2: Minima in Diffraction Pattern
  • Extra Example 3: Diffraction Grating