Physics / Unit 8: Light and Optics
8.6 Color and Dispersion
Notes
White light is a mix of all visible colors.
- Dispersion: a prism separates white light because each color has a slightly different index of refraction. Violet bends the most and red the least. Rainbows form this way in raindrops.
- An object's color is the light it reflects. A red apple reflects red and absorbs the other colors; a white object reflects all; a black object absorbs all.
- Primary colors of light: red, green, blue. Red + green = yellow; all three = white.
- A filter transmits its own color and absorbs others.
Practice
When white light passes through a prism, which color bends the most?
Violet has the highest index of refraction in glass, so it bends the most.
A green shirt is lit with only red light. What color does it appear?
The shirt reflects only green; with no green light to reflect, it looks black.
What color is seen when red light and green light overlap on a white screen?
Adding red and green light gives yellow.
Ready for more? Take the Unit 8 test.