Optical Illusions

1. Optical Illusions • t-Rex is watching you! • Rainbow? • Unlock your car with your brain

2. Ch. 18 - Light 1. Light and Color • Light and Matter • Seeing Colors • Mixing Colors

3. A. Light and Matter • Opaque • absorbs or reflects all light • Transparent • allows light to pass through completely • Translucent • allows some light to pass through

4. B. Seeing Colors • White light • contains all visible colors - ROY G. BIV • In white light, an object… • reflects the color you see • absorbs all other colors ABSORBS ALL COLORS REFLECTS ALL COLORS

5. B. Seeing Colors • The Eye: the retina contains… • Rods - dim light, black & white • Cones - color • red - absorb red & yellow • green - absorb yellow & green • blue - absorb blue & violet Stimulates red & green cones Each eye has 6 – 7 million cones; 120 million rods Stimulates all cones Humans can see 7,000,000 colors.

6. SpectralSensitivity of Cones Rods – “Night Vision” 30 minutes to adjust Peripheral vision 64% 32% 2 - 4%

7. Test for red-green color blindness. B. Seeing Colors • Color Blindness • one or more sets of cones does not function properly

8. C. Mixing Colors Light and color Primary colors are different in art (paint) and in science (light). Science - adds colored lights. ( energy waves) Paint - absorbs(subtracts) colors. ( chemicals) Paint -Primary Colors : red, yellow and blue, (Now, put a Big X thru red, yellow, blue) Science - Light Colors : red, green and blue.

9. Using Pigments, mixing yellow paint with blue paint we obtain … … green...

10. …but by mixing yellow* light with blue light we get… * yellow light =green light + red light … white light!

11. By shining red, green and bluelight beams onto a white screen and making them overlap, we obtain white light.

12. red + blue = Magenta red + green = yellow blue + green = Cyan Cyan, magenta and yelloware the three secondary colors of light Or.... THE PRIMARY COLORS OF PIGMENT!

13. C. Mixing Colors of Light • Primary light colors • red, green, blue • additive colors • combine to form white light • EX: computer RGBs

14. Pixels Pixels : The little dots that come together to form the picture you see. Each pixel can have one specific color depending on the part of the image it represents. Higher # pixels = higher resolution = better picture quality.

15. C. Mixing Colors Light (RGB) Pigment ( CMYK) When mixing pigments, the color of the mixture is the color of light that both pigments reflect.

16. red filter blue filter green filter Optical filters Filter: transparent material that absorbs all light colors except the filter color A filter made of a primary color only allows that color to pass.

17. cyan filter magenta filter yellow filter A filter made of a secondary color transmits the primary colors that make up that secondary color.

18. black filter colorless filter What about a colorless filter or a black filter?

19. Using colored light • If we look at a colored object in colored light we see something different. • For example, consider this outfit: Shirt looks red White light Shorts look blue

20. Red light Shirt looks red • In different colors of light this outfit would look different: Shorts look black Shirt looks black Blue light Shorts look blue

21. By superimposing colored filters (cyan, magenta and yellow) we get the primary colors where pairs of filters overlap. The magenta filter can transmit red and blue. The yellow filter can transmit red and green – Only red can pass through both the magenta filter and the yellow filter. blue green red

22. C. Mixing Colors of Pigment • Pigment • colored material that absorbs and reflects different colors • Primary pigment colors • cyan, magenta, yellow • subtractive colors • combine to form black • EX: color ink cartridges

24. Negative Afterimage - One set of cones gets tired, and the remaining cones produce an image in the complimentary color.

25. Why is the sky blue? Why are sunsets red? Why is the Grass Green?