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Light

Light. Visible Light. Visible Light - the range of frequencies of electromagnetic waves that stimulates the retina of the eye. Visible Light. The lowest frequency of light we can see is red light The highest frequency of light we can see is violet light

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Light

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  1. Light

  2. Visible Light • Visible Light - the range of frequencies of electromagnetic waves that stimulates the retina of the eye

  3. Visible Light • The lowest frequency of light we can see is red light • The highest frequency of light we can see is violet light • EM waves with frequencies lower than red light are called infrared • EM waves with frequencies higher than violet light are called ultraviolet

  4. Sources of Light Sources of Light • Luminous source: emits light waves (Sun, light bulb) • Illuminated source: reflects light waves (Moon)

  5. What happens to the light? • When light waves strike an object, the waves can be: • Absorbed by the object • Reflected by the object • Transmitted by the object

  6. Light and Matter

  7. Transparent • Materials that transmit light waves • Examples: • air • glass • some plastics

  8. Translucent • Transmit light but do not permit objects to be seen clearly • Examples: • lamp shades • frosted glass

  9. Opaque • Transmit no light • Absorb or reflect all light waves

  10. http://www.ted.com/talks/beau_lotto_optical_illusions_show_how_we_see.htmlhttp://www.ted.com/talks/beau_lotto_optical_illusions_show_how_we_see.html

  11. COLOR Color Newton determined that white light was made from a combination of color

  12. Additive Color Mixing • White light = RED LIGHT+ GREEN LIGHT+ BLUE LIGHT • These are considered Primary Light Colors

  13. Adding colors • White light can be split up to make separate colors. These colors can be added together again. Adding blue and red makes magenta (purple) Adding blue and green makes cyan (light blue) Adding red and green makes yellow Adding all three makes white again

  14. Formed by mixing primary colors Yellow Magenta Cyan Secondary Light Colors

  15. Complementary Colors • Two colors that add to produce white light • Cyan and Red • Magenta and green • Yellow and blue

  16. For more practice with mixing colors of light: http://www.physicsclassroom.com/Physics-Interactives/Light-and-Color/RGB-Color-Addition/RGB-Color-Addition-Interactive

  17. Homework Seeing color • The color an object appears depends on the colors of light it reflects. For example, a red book only reflects red light: White light Only red light is reflected

  18. A pair of purple pants would reflect purple light (and red and blue, as purple is made up of red and blue): Purple light A white hat would reflect all seven colors: White light

  19. Filters • A filter can be used to block certain colors of light • Filters allow only certain frequencies to be transmitted. • For additional help with filters go to: • http://www.physicsclassroom.com/Physics-Interactives/Light-and-Color/Color-Filters

  20. Red Filter Magenta Filter Using filters • Filters can be used to “block” out different colors of light:

  21. http://www.michaelbach.de/ot/col_mix/index.html • A cyan filter absorbs red light, the magenta filter absorbs green light, and the yellow filter absorbs blue light.

  22. Making Color by Subtraction • Objects can reflect and transmit light, and they can also filter light. • Colored filters transmit certain frequencies of visible light while absorbing others. • A blue filter absorbs red and green, a red filter absorbs green and blue, and the green filter absorbs red and blue.

  23. Primary Pigment • Pigments are like dyes except they are made of minerals. • Primary pigments absorb only one primary color of light. This means they reflect 2 colors of light. • The primary colors of pigments are yellow, cyan and magenta. • A color printer uses the primary colors of paint to produce any color imaginable.

  24. Secondary Pigments • A pigment that absorbs two colors of light and reflects one is a secondary pigment. • The secondary pigments are red, blue, and green. • The primary pigment colors are the secondary light colors and the secondary pigment colors are the primary light colors.

  25. Complementary Pigments • Red pigment is complementary to cyan. • Blue pigment is complementary to yellow. • Green pigment is complementary to magenta. • Complementary pigments are those that when mixed, result in a black color.

  26. Color Blindness • http://colorvisiontesting.com/ishihara.htm

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

  28. Shirt looks red • In different colors of light these clothes would look different: Red light Shorts look black Shirt looks black Blue light Shorts look blue

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