6D10.10 Double Slit Interference (Young's Experiment)

Shine laser beam through slit to produce interference pattern. Slide has several slit separations. What you see is a combination of 1 and 2 slit patterns. Look at the bright and dark areas of the central maximum to see clearly the two slit pattern.

Setup Requirements: Assembled as needed. Dark room needed. Only center and first order visible from back of large room. Use extra bright laser with separate power supply.

Equations: separation x sin(A)= n x wavelength

Safety Issues: Bright laser has ten times power of pointer.

6D10.12 COMPARE 1 AND 2 SLIT PATTERNS

Arrange 2 red lasers vertically so the top one shines through a single slit in the single slit slide. The lower laser shines through a pair of slits in two slit slide Position screen so both patterns can be seen. The two slit slit interference causes maxima and minima to show up in the central peak of the two overlapping one slit patterns. 

Setup Requirements: Ask ahead of time. Assembled as needed. May conflict with equipment needed for other demonstrations.

Equations: d sin (A) = m x wavelength for two slit interference. a sin (A) = n x wavelength for 1 slit diffraction.

Safety Issues: Lasers in use. Do not point the extra bright lasers at students. You may want to wear the dark glasses while aligning.

6D10.15 Two Source Interference

Shine laser beam on edge of tube to produce interference pattern. Light reflected from outer surface of tube interferes with light reflected from inner surface of tube. Multiple orders can be seen.

Setup Requirements: Dark room needed. Some trial and error needed to position laser correctly. Test tube has 1/2 inch diameter.

Equations: Analysis too complicated to put here.

Safety Issues: Laser

6D20.10 Laser and Grating

Shine laser beam through grating to produce interference pattern.

Setup Requirements: Assembled as needed. Dark room needed. Use extra bright laser with separate power supply.

Equations: separation x sin(A)= n x wavelength

Safety Issues: Bright laser has ten times power of pointer.

6D20.11 Two Colors and Grating

Shine red and green laser beams through grating at same time to show how interference pattern varies with wavelength.

Setup Requirements: Assembled as needed. Dark room needed to see pattern. Use brighter red laser and green PASCO laser.

Equations: slit separation x sin(A)= n x wavelength

Safety Issues: Brightest red laser has ten times power of red pointer. Do not point either laser at students. You may want to use dark glasses while aligning.

6D20.15 White Light and Grating

Shine white light through grating to produce "rainbow" pattern. For a change use CFL instead of incandescent bulb.

Setup Requirements: Assembled as needed. Metal plate with slit inserted where slides go to provide narrow source. Dark room needed. Only center, first, and second order visible from back of large room.

Equations: Separation x sin(A)= n x wavelength

Safety Issues: None

6D20.55 2 Dimensional Interference Pattern

Shine laser beam through student grating to produce 2 dimensional interference pattern.

Setup Requirements: Assembled as needed. Dark room needed.

Equations: slit separation x sin(A)= n x wavelength

Safety Issues: Laser

6D30.10 Newton's Rings

Rings produced by interference can be seen. The pattern is produced by interference between light reflected from a curved upper surface and a flat lower surface. This technique can be use to test if two surfaces are flat.

Setup Requirements: Use an overhead projector,web camera or document camera. If using web camera or document camera put apparatus on dark material. Focus as needed. If using document camera use zoom control. Darken room as needed. Web camera requires software be installed. Look for Applied Vision icon on desktop.

Equations: Radius of a ring = squareroot (R x wavelength x (N-1/2)   R=radius of curvature of lens. N = number of ring counting from center.

Safety Issues: This device is an antique. Handle carefully.

6D30.20 Soap Film Interference

Pattern produced by thin film interference can be seen. A close up view was added to the upper left corner of the photograph.

Setup Requirements: Assembled as needed. Dip cup in soap solution. The soap solution uses Dawn dish washing liquid. To show to a class use the web camera. Software needs to be installed. Look for Applied Vision icon on desktop. After dipping cup in soap solution put in "fingers". Place camera lens near cup and adjust to show colorful pattern on monitor. Either way the soap film has a short lifetime. Dip in soap solution again as needed. Dim room lights as needed.

Equations: Condition for minimum is 2 x thickness = m x wavelength

Safety Issues: None

6D40.10 Michelson Interferometer

Pattern produced by interference of light beams traveling in perpendicular directions can be seen. Use as visual aid in describing Michelson-Morley experiment.

Version shown damaged. This demo not available Spring 2015. Try again in the Fall.

Setup Requirements: N/A

Equations: If the movable mirror is moved a distance x, then the wavelength = 2x/m where m is number of fringes that move past a point as the mirror is moved.

Safety Issues: Laser. Fragile optical device.