Definition for two sources of traveling waves with the same frequency separated by some distance. Conditions for constructive and destructive interference; nodes and maxima; interference patterns.

Creating an interference pattern in a pool of water by tapping on the surface at two points. Also includes a slide of a butterfly in a pond.

Conditions in terms of angle θ between the center of the two sources and the point at which the interference is being measured.

Finding locations in the lecture hall where constructive and destructive interference occurs from two speakers placed at the front of the room.

The original experiment used to demonstrate that light was a wave, performed here by shining a red laser through two small slits.

Comparing interference patterns for red, blue, and white light, including a slide showing all three.

Tracking the interference pattern from two sources of radar waves using a receiver that slides along a track.

Conditions for constructive and destructive interference for light shining through N slits.

Interference pattern for a red laser and a white light shining through a fine grating.

Using a lens to see an interference pattern at a much closer distance. Demonstration uses the lens of the eye and an individual grating to view the pattern for a white light and a neon light.

Definition, with conditions for maxima and minima of this single-slit interference and a plot of the diffraction pattern.

Showing that for a narrower slit the diffraction pattern becomes wider using a variable width slit and a green laser.

Diffraction for a circular opening, and discussion of angular resolution for distinguishing between two light sources. Includes the Rayleigh criterion and discussion of angular resolution for telescopes on earth and in space.

Testing the eye's angular resolution by looking at a series of pairs of pinholes with different separations to see which ones appear as two distinct light sources.

Introduced as a method for measuring the small wavelength of visible light. Diagrams and link to a visualization illustrating interference from light passing through two slits. Definition of and conditions for interference. Constructive vs. destructive interference. Phase shifts, iridescence, and extra paths; all with equations and diagrams.

Equations and diagrams for calculating the interference from two sources, using examples of microwaves and visible light.

Definition, with diagrams. Equations and diagrams for single slit diffraction and double slit diffraction/interference. Statement of Babinet's Principle.

Equations for a traveling sine wave, electromagnetic waves, interference, and diffraction

Finding the number, width, and separation of slits given a picture of a diffraction pattern of red light.

Definition, with diagrams of constructive and destructive interference. Two-slit interference and diffraction are defined with equations and diagrams.

Superposition of waves; double-slit and triple-slit experiments with intensity distributions and wavelengths.

Double-slit experiment, phase difference, interference, and intensity in diffraction.

Six questions with answers and explanation.

Finding angular resolution for single telescope, then two telescopes as interferometer.

Solution (PDF)

Finding angular resolution for ground-based and space-based telescopes.

Solution (PDF)

Applet showing the propagation of waves in two dimensions to illustrate the properties of interference, diffraction, and reflection.