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Light & Electromagnetic Radiation

Light & Electromagnetic Radiation. Ch. 19. Electromagnetic Radiation. Electromagnetic waves are transverse waves created by the motion of electrically charged particles Radiation is the transfer of E by electromagnetic waves. Electromagnetic Radiation. Do not need a medium to transfer E

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Light & Electromagnetic Radiation

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  1. Light & Electromagnetic Radiation Ch. 19

  2. Electromagnetic Radiation • Electromagnetic waves are transverse waves created by the motion of electrically charged particles • Radiation is the transfer of E by electromagnetic waves

  3. Electromagnetic Radiation • Do not need a medium to transfer E • Can travel up to 300,000 km/s (light speed) • Slows down when it passes through matter (s, l, g) but still travels much faster than sound or water waves.

  4. Electromagnetic Radiation • In a vacuum: • All EM waves travel at the same speed • Frequency and wavelength vary • Remember: as frequency increases, wavelength decreases

  5. Light • Light either passes through, is absorbed by, or bounces off of an object, depending on what it’s made of: • Opaque materials • Absorb or reflect all light • Cannot see through them • Example: heavy curtains

  6. Light • Translucent Materials • Allow some light to pass through • Cannot clearly see objects through them • Examples: frosted glass, sheer curtains, waxed paper

  7. Light • Transparent Materials • Allow light to pass through • Clearly see objects through them • Example: glass windows

  8. Light • Color • Why are blue jeans blue? • Blue jeans absorb all colors except blue. The blue light is reflected back to your eyes.

  9. Light • White • Reflecting all colors – ROYGBV (red, orange, yellow, green, blue, violet) • Black • Absorbs all colors, reflects none back to your eyes

  10. Light • How do you actually see color? Night vision Rods Light Retina Cones Absorb color Detailed shapes Photoreceptor Cells

  11. Light • Cone cells – 3 types: • Red, blue, and green (primary colors of light) • Each “measures” the amount of that color of light, and they combine signals to tell your brain the color you’re seeing

  12. Color • Pigments • Absorb some colors and reflect others • Used to create materials that absorb all colors except the one we want • Color we want is reflected • Examples: dye, ink, paint

  13. Color • Filters • Transparent material that transmits one or more colors of light but absorbs all others • Color we want is let through • Color of filter is the same as the color it transmits

  14. 2 Types of Color • Additive • Primary colors – R, G, B • Adding light of different colors to create all colors • Additive because R + G + B = white • (Colors add to form white, a color that reflects all others)

  15. 2 Types of Color • Subtractive • Primary colors yellow, magenta, cyan • Adding pigments so that more color is absorbed and less is reflected • Subtractive because Y + M + C = black • (Colors combine to formblack, a color that absorbs all others)

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