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.

Introduces constructive and destructive interference that arise from superposing coherent, monochromatic waves with a phase difference.

Shows the setup of the double slit experiment and uses the geometry to determine the interference pattern from the phase difference of the waves.

Introduction to Huygens's Principle, where every point on a wavefront acts as a source of spherical waves, and shows how this makes diffraction patterns possible; defines Fraunhofer diffraction.

Calculates the interference pattern of a single finite slit due to Fraunhofer diffraction.

Shows qualitatively the patterns that arise from many-slit diffraction gratings, and the pattern dependence on the number of slits.

When an unknown slit pattern is illuminated with red laser light, it produces the illustrated interference fringes; what are the width and/or separation of the slits? Solution is included after problem.

How many interference maxima lie within a given angular range in a two-slit interference setup? Solution is included after problem.

Find various relationships between phase difference, path length difference, and screen position for a two-slit interference setup. Solution is included after problem.

Coherent light is incident from an angle onto a plane containing two slits; find the relationship between the incidence angle, d, λ, and the screen position angle for a point that is an interference maximum. Solution is included after problem.

Determine the wavelength of light in a two-slit interference setup based on the setup geometry and the distance between the central maximum and the second-order bright fringe. Solution is included after problem.

Conceptual questions about the conditions for interference and how two-slit and finite-slit interference patterns depend on setup parameters.

For a two-slit interference setup with given parameters, find the spacing between adjacent fringes and the position of the third order bright fringe.

How many bright fringes are in the central diffraction maximum of the interference pattern from two finite slits?

Confirm the condition for the positions of interference maxima in a three-slit interference pattern, and find the spacing between adjacent maxima.

In a two finite slit diffraction pattern, characterize the relationship between slit width and separation based on the number of bring fringes in the central diffraction maximum.

Distinguish constructive and destructive interference of illustrated waves.

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.