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Light and Color

Light and Color. Chapter 27 and 28. Nature of Light. Both a wave and a particle Electromagnetic wave Photon Wave/Particle Duality (Quantum Physics) Speed of Light (c) = 300,000,000 m/s (186,000 mph) Light-year = Distance light travels in one year

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Light and Color

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  1. Light and Color Chapter 27 and 28

  2. Nature of Light • Both a wave and a particle • Electromagnetic wave • Photon • Wave/Particle Duality (Quantum Physics) • Speed of Light (c) = • 300,000,000 m/s (186,000 mph) • Light-year = • Distance light travels in one year • Light is created by vibrating electrons (charges)

  3. Electromagnetic waves • Broken into Electromagnetic Spectrum

  4. Transparent/Opaque Materials • Transparent: light passes through (waves re-emmited) • Opaque: light does not pass through (waves absorbed) • Different materials = slower speed of light • Materials can be transparent to some frequencies of light and opaque to others • Glass: • Visible Light = transparent • Infrared/Ultraviolet = opaque (not transparent)

  5. Shadows • Ray: a beam of light • Light is considered a bundle of rays • Shadow: when an object blocks some rays • Umbra: total shadow • Penumbra: partial shadow (some light from reflections or alternate source fills in the shadow)

  6. Polarization • Light = transverse waves • Wave is oriented by how electron vibrates • Orientation of wave = polarization • Most sources are not polarized (all different angles)

  7. Polarization Con. • Polarization filters block all light not same angle as filter • Glare (reflection) from horizontal surfaces tends to polarize that way • Vertical filter would block it • 3-D viewing (each eye has different polarization filters)

  8. Color Spectrum • White light = all colors • Red • Orange • Yellow • Green • Blue • Indigo • Violet • Black = absence of light

  9. Color by reflection • We see the color reflected by an object • Other colors are absorbed • Color of light can influence color seen (by lack of certain colors)

  10. Color by Transmission • Color transparent materials are opaque to all colors but the color they seem • For example: blue glass lets blue light through but absorbs all other colors

  11. Sunlight • Mostly white: but stronger in the yellow/green areas and weaker on the ends • This makes natural sunlight yellowish

  12. Colored Light • Red Light + Green Light + Blue Light = White Light • Red + Blue = Magenta • Blue + Green = Cyan • Red + Green = Yellow • Magenta + Cyan + Yellow = White • Any color can be made by mixing these three colors at different brightness • Complementary mixed = white

  13. Pigments • Pigments mix to black • Pigment is color of light (or mix) that is reflected • Blue reflects Green/Blue/Violet (absorbs the rest) • Yellow reflects Red/Orange/Yellow/ Green (absorbs the rest) • Green reflects just Green (only color both yellow and blue reflect)

  14. Why is…? • Sky Blue? • Atmosphere acts like a prism and scatter the sunlight, Blue scatters the most so that is what we see • Sunsets Red? • Thicker atmosphere scatters light more, red gets scattered most • Water Greenish-Blue? • Water absorbs colors as it gets deeper • Red/orange/yellow absorb at shallow water • Green/blue/indigo/violet absorb at deeper levels

  15. Atomic Spectra • Every element gives off specific colors when heated • Spectroscopes analyze the exact colors to identify exact elements

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