This experiment uses the laser and white light combination Michelson interferometer setup. Because alignment requires a laser, this demonstration will be delivered (and can be used) with a laser installed. White light from a bright point source is collimated by a condenser lens and passes through a heat filter directly into the interferometer. The light exiting the interferometer is focused onto a distant screen, providing a field about one foot in diameter, clearly visible over the entire lecture hall. The fringe colors can be seen to be negative colors, that is, complementary colors to the colors to the spectral colors which are eliminated by destructive interference.

The photographs above show some of the color patterns using this interferometer.

This demonstration is very sensitive to alignment and temperature, and is not recommended for routine classroom use.

This is a dielectric coating with an index of refraction between that of air and glass, that covers one-half of the glass plate. If the coating is one-quarter wavelength thick for yellow light it prevents reflection of yellow light because the reflections from the two surfaces are exactly out of phase.

Light from a bright point source with a condenser lens and iris is focused by a 20 cm focal length convex lens through a glass plate onto a distant screen. In the photos above the glass plate reflects some light which is reflected a second time by a front surface mirror to form a spot to the right of the direct beam from the bright point source.

With no anti-reflective coating (left above) the direct beam is less intense because of the reflected beam. When the anti-reflective coating is raised into the beam (right above) the direct beam is more intense and the reflected beam is less intense. When the yellow filter is used the beam reflected by the anti-reflective coating is slightly magenta colored, because the thickness of the coating is not quite one-quarter wavelength for the extreme colors of the spectrum.

These filters are glass plates that contain a series of equally spaced high refractive index dielectric layers. The layers reflect light of a particular wavelength, leading to destructive interference, so the reflected and transmitted light are complementary colors. The filter is labeled by the transmitted color, so a red filter transmits red and reflects cyan, a yellow filter reflects blue, a green filter reflects magenta, and a blue filter reflects yellow. To facilitate re-mixing and display, the spacing of the reflective layers in these filters are designed for light incident at 45 degrees.

In the photographs above the direct beam is at the left and the reflected beam is at the right. The reflected beam from the red filter (left) is a bit saturated, so the cyan coloring is not readily visible.

A Bright point source of light at the right illuminates a soap film in the wire ring. The transmitted light is seen at the left and the reflected light at the rear between the light source and the wire ring. Note that the reflected and transmitted colors are complements, although the transmitted light is desaturated by the white light background, as seen above.

After a while the top section of the film becomes less than one-quarter wavelength thick, so the waves reflected from the front and rear surfaces of the film are out of phase, resulting in no reflected light.

Two crossed polaroids, oriented vertically and horizontally, are placed in front of a goose-neck lamp, thereby preventing light from passing to the viewers. When a third polaroid is inserted between the two crossed polaroids at an angle of 45 degrees with respect to the original axes, light can be seen passing through the system.

This demonstrates that the electromagnetic field of which the light consists is a vector. The diagonal polaroid passes a component at 45 degrees with respect to the original light, and the second polaroid passes a component at 45 degrees with respect to the diagonal polaroid. The component of a component is actually perpendicular to the axis of the second original polaroid.

The real paradox involving this system involves an analysis of single photons. How can a single photon originally polarized parallel to the first polaroid have its angle of polarization rotated 90 degrees and exit the final polaroid polarized perpendicular to its original plane of polarization?

Compare M7-03, a simpler demonstration using only two polarizing filters.

When sunlight reflects off a horizontal dielectric surface such as water in a lake, wet roads, or even dry smooth roads, the reflected light is largely horizontally polarized. Polaroid sunglasses are oriented vertically so they remove "glare," which is horizontally polarized specular reflection from such surfaces.

Position the point source so that it reflects from the lecture table onto the front white screen at about the Brewster angle. Rotating a polaroid in the light from the point source before reflection shows clearly that the reflected light is polarized. Individually viewing the reflected light directly using a polarizing filter demonstrates the value of polaroid sunglasses in removing glare. Placing a piece of aluminum foil where the light hits the table demonstrates that reflection from a conducting surface is not polarized.

The photographs above show the polarization axis (a) parallel and (b) perpendicular to a dielectric surface, and (c) parallel and (d) perpendicular to a conducting surface (a sheet of aluminum foil).