1. Warm Up Between Red or Blue light, which has a larger
Wavelength
Frequency (energy)
Compared to “C” is the star “1” moving towards us or away?
You have a horizontally aligned polarizing filter. Explain how to position a second polarizing filter so that no light comes through.

2. Color and Vision
When all the colors of the rainbow are combined, we see "white light".

3. How we see the color of things
The light that reaches our eyes from an object can be:
Emitted directly from the object (light bulb or glow stick)
Reflected by the sun or other light source

4. How we see other colors
The three color receptors in the eye allow us to see millions of different colors.
The additive primary colors are red, green, and blue.
All the different shades of color we can see are made by changing the proportions of red, green, and blue.

6. Magenta light on a green surface appears colorless because magenta is absorbed
Green light on a magenta surface appears colorless because green is absorbed
Magenta in
Green in
No color
No color
Magenta surface
absorbs (subtracts)
green.
Green surface
absorbs (subtracts)
red and blue (magenta).

7. Practice
White light shines on an object that appears red. Draw a diagram of the three primary colors hitting the object, and the appropriate colors being absorbed or reflected.
Magenta light shines on an object that appears red. Draw a diagram of the primary colors of light being absorbed or reflected.

8. Why are plants green?
Plants absorb energy from light and convert it to chemical energy in the form of sugar (food for the plant).
Chlorophyll is an important molecule that absorbs blue and red light.

9. Color By Subtraction
Colored dyes get color from a subtractive process.
Chemicals, known as pigments, in the dyes absorb some colors
Colors that are not absorbed are reflected, and you see them
Magenta, yellow, and cyan are the three subtractive primary colors.

11. How the human eye sees color
Photoreceptors in the retina (back of eye) send chemical signals to the brain
optic nerve

12. Photoreceptors in the eye
Cones respond to three colors: red, green and blue.
Rods detect intensity of light: black, white, shades of gray.

13. How we see colors ENERGY determines the chemical signal that is sent
If the brain gets a signal from ONLY green cones, we see green.

14. Color and Vision
We can think of different colors of light like balls with different kinetic energies.
Blue light has a higher energy than green light, like the balls that make it into the top window.
Red light has the lowest energy, like the balls that can only make it to the lowest window.

15. 16.2 How does a color TV work? Televisions give off light.
To make color with a TV, you can use red, green, and blue (RGB) directly.
The screen is made of tiny red, green, and blue dots.
The dots are called pixels and each pixel gives off its own light.
TV sets can mix the three colors to get millions of different colors.

16. Application: Color Printing