Understanding Light and Color: The Spectrum, Reflection, and Pigments

1. Color

2. Isaac Newton first studied light when he used a piece of glass and first saw the color spectrum.

3. The visible/color spectrum is the ordered arrangement of colors by wavelength and frequency

4. Spectrum

5. Color by Reflection • Different objects reflect (if material is opaque) and absorb (if the material is transparent)

6. Color by Transmission • The color of a transparent object depends on the color of the light it transmits • The material in glass that selectively absorbs colored light is pigment. • Glass is colorless since it transmits all visible frequencies.

7. Light-there are primary and secondary colors of light Primary-Red, Blue, Green (examples-the 3 pixels in your TV) • Secondary-the result of mixing 2 primary colors Red + Blue = Magenta Blue + Green = Cyan Red + Green = Yellow

8. Adding colors of light is called Color by Addition • White-addition of all colors of the visible spectrum, or by adding the 3 primary colors • Black-absence of light, all 3 lights are blocked

9. ADDITION OF PRIMARY COLORS • When paints or dyes are mixed, the mixture absorbs the frequencies of the paint or dye

10. Complementary colors of light-two colors which when added, create white light • Blue + Yellow = White • Red + Cyan = White • Green + Magenta = White So…yellow light is the complementary color to blue light

11. A Pigment is a colored material that absorbs certain wavelengths of light (certain colors) and transmits or reflects others---Think PAINT

12. Primary Pigment-A pigment that absorbs only one primary color from white light Yellow (absorbs blue light) Cyan (absorbs red light) Magenta (absorbs green light)

13. Secondary Pigment-A pigment that absorbs two primary colors and reflects one Red (absorbs green & blue) Blue (absorbs red & green) Green (absorbs red & blue)

14. PRACTICE

15. Answers to Practice • Addition of Primary Colors • Red + Green = Yellow • Red + Blue = Magenta • Blue + Green = Cyan

16. Color by subtraction~the pigment is ‘taking out’ / ‘subtracting’ / ‘absorbing’ a color of light • Complementary Pigments-two colors that when added, will absorb all colors of the spectrum (‘black’ pigment is made) minimal/no light is reflected

17. Think Mixing Paint… yellow + blue = black cyan + red = black magenta + green = black

18. PRACTICE

19. Answers to Practice • Practice A- Magenta is red + blue. Blue is subtracted (absorbed) so that leaves red, shirt appears red • Practice B-red is a primary color, blue is subtracted (absorbed) so it is not present, so shirt appears red • Practice C-Blue is a primary color, blue is subtracted (absorbed) so no color is left, shirt appears Black

20. Why? • …is the sky blue • Blue is scatted the most during the middle of the day, due to its high frequency and low energy • …are sunsets red • Red, orange, and yellow are scattered more during this time, so red is refracted more, so red, orange, etc if seen

21. Do problem set in class