Chapter 16.2 Notes

Materials that transmit all light waves with little or no distortion are called transparent.

Materials that transmit some light waves with some distortion are called translucent.

Materials that absorb or reflect light waves are called opaque.

Primary and secondary colors of light

The color of light is determined by its wavelength (and frequency).

• Red light has the longest wavelength
• blue light has the shortest wavelength.

White light is a combination of light; when blue, red, and green light is combined we get white light.

Red, blue, and green are often called called the primary colors of light. By definition, any combination of colors that produce white light are primary. The making of white light from others colors is known as an additive process. This is about transmission of various light waves from an original source directly to the retina of your eye and it's subsequent interpretation by our brains.

Mixing any two of the primary colors produces one of the secondary colors of light.

• Red + Blue produces Magenta
• Red + Green produces Yellow
• Blue + Green produces Cyan

Take a look at this page for more on colors of light and the color wheel model.

Do not confuse light with pigments. Paints are mixed by a subtractive process. Pigments are chemicals that have the ability to absorb, that is subtract, every wavelength EXCEPT the one for the color you are interested, which the pigment reflects. In painting, we get black if we mix all the different colors together.

Check out this page to mix light in an ADDITIVE form, as though you were shining light of the various primary and secondary colors on a screen. A browser that can handle JAVA is necessary. Most "4.0" or later browsers can do this.

AND then check this page to see what happens in a SUBTRACTIVE condition, as though light is FILTERED through prisms of each of the colors.

Polarization of Light

Polarization of light demonstates that light waves travels as transverse waves, not longitudinal waves. The word polarization means in "one direction". Using the rope model, if you shake a rope from side to side a transverse wave is produced; we then say that the wave is polarized in the horizontal direction. If you shake the rope up and down a transverse wave is produced; we then say that the wave is polarized in the vertical direction. According to this theory, if you place a polarized filter in front of a light only part of the light will get through; if next you place another filter at right angles to the first filter- all the light will be blocked out. This experiments demonstrates that light behaves as a transverse wave .

Glossary of Terms

demonstrations: polarized light filters, secondary color filters, and computer model of primary colors. Short internet study.

additional internet sources:

Explorescience.com has some interesting activities in optics. You will need the Shockwave plugin for your browser to view them.