Conceptual Physics Alive: Light & Color, Reflection & Refraction, Light Waves
Paul Hewitt teaches about Light & Color, Reflection & Refraction and Light Waves.
Master teacher Paul Hewitt teaches non-computational Conceptual Physics. Observe Hewitt teach in a classroom with real students, using engaging demonstrations and artwork.
DVD Includes 3 Episodes:
Episode 1: Light and Color: The electromagnetic nature of light and the reason its speed changes when passing through transparent materials are explained. Several demonstrations illustrate the addition of different colors of light. Finally, the colors of everyday things such as the sky, sunset, and ocean are discussed. Segment length: 40 minutes
Episode 2: Reflection and Refraction: Mirrored and diffuse reflection are compared. Refraction is demonstrated using a water tank. The concepts of total internal reflection and light dispersion are discussed, leading to a demonstration of properties of a rainbow. Segment length: 41 minutes
Episode 3: Light Waves: The interference of light waves is demonstrated with laser light, and related to the colors of thin films. A discussion on polarization is illustrated using polarizing material. Segment length: 30 minutes
Light and Color Includes:
• Begins with an electromagnetic explanation of light waves.
• Light frequency range: from red, then orange ... to violet, and then to ultraviolet.
• X rays: high frequency E&M radiation.
• Prism is shown, and leads to discussion of how light slows down when passing through a transparent material.
• Toy soldier analogy of light passing through glass.
• Explanation of different colors traveling at different average speeds through transparent materials.
• Graph of frequency versus brightness shown on chalkboard.
• Brightest color from the sun is yellow-green.
• Examples of yellow-green fire engines and street lights.
• Red, green, and blue parts of the spectrum are shown on the graph.
• Light box shows overlapping of red, green, and blue to produce white. Complementary colors are also shown and discussed.
• Cyan color of seawater explained.
• Demonstration of three lamps, red, green, and blue, mounted on lecture table shine in succession on Hewitt to produce beautiful shadows.
• Light box shows that sky blue and sunset orange are complementary colors.
• Why sky is blue is explained in terms of scattering.
• Tuning forks at opposite ends of lecture table illustrate light from the sun traveling to the earth 's atmosphere. Hewitt with assistant Meidor shows why sunsets are orange.
• Chalkboard explanation of blue sky and orange sunsets.
• Whiteness of clouds.
• Green flash.
• Bluish color of distant dark mountains.
• Yellowish color of distant bright mountains.
Next-Time Question: Why do we look upward and see a blue sky, while astronauts in orbit looking down through the same air don't see the blueness of the sky at all? [We look upward at a blue sky against the black background of outer space. Even a faint color seen against a pitch-black background appears bright. The astronauts, however, see the same faint blue against a bright background - the light reflected from the earth's surface. Light from the earth's surface overwhelms the faint blue, which is not seen.)
Reflection and Refraction Includes:
• Hewitt begins with the game 'Fermat's Principle of Least Time' (which is in the college edition of Conceptual Physics, but not in the high school version).
• The principle of reflection; the angle of incidence equals the angle of reflection.
• Diffuse reflection for rough surfaces.
• On the chalkboard Hewitt draws a candle in front of a mirror and sample light rays to illustrate the law of reflection.
• Refraction is illustrated on the chalkboard by Fermat's principle of least time, and the case is given of a lifeguard wanting to save someone in distress in the waterthe path of shortest time is not necessarily a straight line.
• Refraction and changes in light speed when going from one medium to another.
• Demonstration of wheels rolled down an inclined plane that bend when they roll from a smooth surface to a rough surface.
• Chalkboard sketch of wheel action, and how light similarly bends in going from air to water.
• Demonstration of the refraction of "root beer" poured in a mug.
• Hewitt tells of seeing a bottle of Coke embedded in plastic where very little refraction occurred. This allowed a 'truer" view of the amount of Coke in the bottle.
• Demonstration (Hewitt's first!) in response to a student question. A tank of water is produced and the 'Coke bottle' phenomenon is nicely displayed.
• Demonstration of refraction of a laser beam in water.
• Hewitt suggests an experiment in the bathtub wherein a flashlight is tipped upward to reach the critical angle.
• Critical angle of light in water.
• Fiber optics, and the hair of polar bears.
• Rainbows and prisms.
• Demonstration of the rainbow's bow shape with a set of sticks that simulate light rays.
• Fisheye view of sky.
• Nearsightedness in water.
Next-Time Question: What is the minimum size of a plane mirror on the wall to see your full-length image? What effect does distance have on your answer? (A mirror half your height will give you a full view of yourself, regardless of distance. So distance does not affect the size needed.)
Light Waves Includes:
• Hewitt begins with the beautiful colors of Peacocks feathers Soap bubbles Abalone shells Gasoline on a wet street.
• Interference colors.
• Demonstration of wave interference by irregular surfaced glass in the beam of a laser.
• Chalkboard sketch explanation of laser interference.
• Chalkboard sketch explanation of the colors from gasoline on a wet street.
• Skit about watching the colors of bathtub soap bubbles.
• Coated camera lenses.
• Polarization of the action of ropes vibrating within the slats of a fence.
• Polarization of light waves.
• Demonstration of Polaroid filters.
• Edwin Land's fashioning of the first Polaroid filters.
• Demonstration of a pair of Polaroids crossed to show light blockage.
• Vector nature of light reviewed.
• Polarized sunglasses
• Polaroid glasses for 3-D viewing.
Next-Time Question: A pair of crossed Polaroids will not pass light. But when a third Polaroid is inserted at an angle between the pair of crossed Polaroids, light emerges. Why? (Light polarized at goo to a Polaroid filter will not pass through the filter, which is why light will not pass through a single pair of crossed Polaroids. But when a third Polaroid at a non 90° angle is sandwiched between, the light vector that emerges through the first filter falls on the inserted Polaroid at a non 90° angle. So some passes through the inserted Polaroid. This vector in turn falls on the last Polaroid at a non 90° angle, so some of this emerge JS to be the light seen.]