Light & Color

1. Light & Color Light Part 3

2. Color • Not in things themselves • Provoked by the frequencies of light emitted or reflected by things

3. Newton • Studied colors created by passing sunlight through a prism

4. Newton • White Light  under which white objects appear white and colored objects appear in their individual colors ie: Sunlight • White is the combination of all of the colors of light, but not a color itself • Black is also not a color, but instead the absence of light

5. Colors of Objects • Due to the way the objects reflect light • As light strikes an object the electrons in the object are forced into vibrations • Once vibrating these electrons send out their own energy waves in all directions

6. Colors of Objects • If the vibrations are at resonant frequencies  light is absorbed • If the vibrations are above or below resonant frequency  light is re-emitted or passes back into the medium from which it came (reflection) • Objects can only reflect frequencies of light which are present in the illuminating light

7. The Sun • Brighter in mid-frequency yellow & green regions • Higher and Lower frequencies are less bright • Reason yellow and bright red vehicles stand out

8. Mixing Colored Light • Red low frequency • Green  middle frequency • Blue  high frequency • Red + Green + Blue  White • Any color can be made by overlapping these three colors and adjusting the brightness of each

9. Mixing Colored Light • Red + Blue Magenta • Red + Green  Yellow • Blue + Green  Cyan

10. Complementary Colors • Any two colors of light that when added together produce white light • Blue + Yellow White • Red + Cyan  White • Green + Magenta  White

11. Pigments • Mixing pigments or dyes does not produce the same effect as mixing colored light • Are materials that selectively absorb colored light

12. Why is the sky blue? • Scattering of light by the particles in our atmosphere causes the particles to vibrate • During the day light takes a shorter path through the atmosphere causing the particles to vibrate at a higher frequency

13. Why are sunsets red? • During sunrise and sunset the light from the sun takes a longer path through the atmosphere • This now causes the scattered light to vibrate at a lower frequency