Optics

6A - Geometric Optics

44. Total Internal Reflection

6A44.1 Total Internal Reflection in Water
A beam of light shines onto a mirror in an aquarium. The mirror reflects the beam toward the surface, and the angle of the mirror can be adjusted gradually so that one sees refraction, refraction and partial reflection, critical angle, and total internal reflection. As the angle of the beam approaches the critical angle, one also sees dispersion as the refracted beam spreads into a spectrum on the screen.
[Set-Up Time: 20 min.]
[Current Condition: Good]

6A44.2 Light Pipe, Fiber Optic Cables
A laser shines into a long, curled light pipe and emerges at the other end. Stranded fiber optic cable is also available. Dipping a solid fiber into baby oil will "release" the beam.
[Set-Up Time: 5 min.]
[Current Condition: Good]

6A44.? Bucket of Light
A laser beam follows the arc of a stream of water, and is not "released" until it reaches the collection bucket.
[Set-Up Time: 15 min.]
[Current Condition: Good]

60. Thin Lens

6A60.1 Optics "Blackboard"
A large magnetic board with a fixed source of parallel light rays can be used to demonstrate geometric optics. Components include: flat mirrors, curved mirrors, thin lenses, thick lenses, transparent rectangular solids, and a prism.
[Current Condition: Good]

65. Thick Lens

6A65.1 Fresnel Lens
The flat plastic lens from the surface of an overhead projector can be used for comic effect when held directly in front of the speaker's face.
[Set-Up Time: 5 min.]
[Current Condition: Good]

6B - Photometry

10. Luminosity

6B10.30 Paraffin Block Photometer
Two light sources, one twice as strong as the other, are placed a meter apart. Two paraffin blocks with a sheet of aluminum foil sandwiched between them form a photometer; move the photometer between the light bulbs until the brightness on each half appears equal. One can extrapolate the inverse square law of luminosity.
[Set-Up Time: 10 min.]
[Current Condition: Unknown]

30. Radiation Pressure

6B30.1 Radiometer (Not!)
The spinning radiometer used in 4B40.1 Radiation of Heat does not demonstrate radiation pressure, as often thought. Shining a flashlight on it will push the black sides of the vanes, rather than the reflective sides, indicating that the spinning is due to heating and expanding the very small amount of gas inside, and not due to momentum transfer of photons. The effect of radiation pressure is many orders of magnitude smaller and requires a much more sensitive measuring device to detect.
[Set-Up Time: 5 min.]
[Current Condition: Unknown]

40. Blackbodies

6B40.35 Good Radiator/Bad Radiator
A white tile with a black circle on it is heated in a furnace until glowing. The black circle glows brighter than the surrounding tile.
[Set-Up Time: 30 min.]
[Current Condition: Untested- should be good]

6C - Diffraction

10. Diffraction Through Slits

6C10.1 Single Slit Diffraction
A glass slide containing a variety of single slits of different widths (as well as double slit and grating configurations) can be placed in front of a laser, and the diffraction pattern viewed on the screen.
[Set-Up Time: 5 min.]
[Current Condition: Good]

20. Diffraction Around Objects

6C20.1 Poisson's Spot (Arago's Spot)
A small circular object is placed in front of a laser beam, and the diffraction pattern, with a bright spot in the very center of the shadow, is observed on the screen. Note: this is hard to see in a large class unless students are allowed to come closer to the screen.
[Set-Up Time: 10 min.]
[Current Condition: Good]

6D - Interference

10. Interference from Two Sources

6D10.1 Double Slit Interference
A glass slide containing a variety of double slits of different widths and separations (as well as single slits and grating configurations) can be placed in front of a laser, and the interference pattern viewed on the screen.
[Set-Up Time: 5 min.]
[Current Condition: Good]

See also: 3B60.1 Beats with Tuning Forks.

20. Gratings

6D20.1 Interference with a Grating
A glass slide with a variety of different grating configurations can be placed in front of a laser, and the interference pattern viewed on the screen.

(see images above in 6D10.1)
[Current Condition: Good]

30. Thin Films

6D30.1 Newton's Rings
A convex lens held against flat glass is placed in the way of a beam of light. The reflected light shows circular interference fringes due to the varying thickness of the air gap between the pieces of glass.
[Set-Up Time: 10 min.]
[Current Condition: Good]

Setup:

Display on Screen:

6D30.2 Soap Film Interference
White light is reflected off of a thin film of soap, showing black at the thinnest part and different colors at other parts of the film of different thickness. The film gradually gets thinner until it pops.
[Set-Up Time: 25 min.]
[Current Condition: Good]

Setup:

Display on Screen:

6F - Color

30. Dispersion

6F30.1 White Light and Prism
A beam of white light shining on a prism produces the rainbow spectrum on a screen.
[Set-Up Time: 10 min.]
[Current Condition: Good]

Display on Wall:

40. Scattering

6F40.10 Sunset
A few drops of milk in a beaker of water is illuminated from the back with a flashlight. Color scattering is observed.
[Setup time: 10 mins.]
[Current Condition: Good]

6H - Polarization

10. Dichroic Polarization

6H10.1 Light Beam and Three Polaroid Filters
Send a light beam through a single polaroid filter (with a large arrow indicating the polarizing axis), then use a second polaroid filter to show that the beam is now polarized, and can be completely blocked if the second polarizer is set perpendicular to the first. Insert a third polarizer between the two, and show that some of the light beam is restored.
[Set-Up Time: 5 min.]
[Current Condition: Good]

20. Polarization by Reflection

6H20.1 Brewster's Angle
There is no standard demo for this, but it can be done either by reflecting a light beam off a metallic sheet and examining the reflected ray with a polaroid filter, or by polarizing a laser beam, reflecting it off a glass surface, and rotating the angle of incidence until the reflected ray disappears.
[Set-Up Time: Unknown]
[Current Condition: Good]

30. Circular Polarization

6H30.40 Rotation dispersion in corn syrup
A beaker of corn syrup is placed between crossed polaroids on the overhead. The corn syrup changes colors as the second polaroid is rotated.
[Setup time: 10 mins.]
[Current Condition: Good]

6H30.80 Faraday Effect
Polarized laser light passes through a solenoid filled with toluene. When the solenoid is turned on, the polarization of the outgoing beam is rotated proportionally to the strength of the magnetic field.
[Setup time: 15 mins.]
[Current Condition: Good]

35. Birefringence

6H35.15 Birefringence on the overhead
A calcite crystal over a sheet with large lettering makes a double image. Each image has a different polarization.
[Setup time: 5 mins.]
[Current Condition: Unknown]