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Light

Light. Chapter 16. Mission. In this presentation, we will do the following: define light. tell how light is measured. tell how light travels. explain the electromagnetic spectrum. tell how light is transferred. tell how colors are formed.

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Light

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  1. Light Chapter 16

  2. Mission In this presentation, we will do the following: • define light. • tell how light is measured. • tell how light travels. • explain the electromagnetic spectrum. • tell how light is transferred. • tell how colors are formed. • tell some applications of light in industry and everyday life.

  3. 16.1 Light Fundamentals • Light - EM wave (transverse) that human eye can see. • Different light wavelengths are seen as different colors. • Ray - straight line representing path of beam of light. • Ray optics - ray diagrams to study travel of light.

  4. EM Spectrum The electromagnetic spectrum includes, from longest to shortest: • radio waves • microwaves • infrared • Visible light • ultraviolet • X-rays • gamma-rays

  5. Transference of Light • Can be reflected, absorbed, refracted, transmitted. • To be black, all wavelengths of light hitting that object are absorbed; no light is reflected. • Solid objects, for the most part, will reflect light. • Transparent objects will transmit light through them.

  6. The Speed of Light • Galileo - 1st to say that light had finite speed • Ole Roemer - 1st to take data from which speed of light could be measured • A. A. Michelson - 1st American to win Nobel prize measured speed of light

  7. Use of laser allows for new way of measuring speed of light. • Speed of light, c, is 299,792,458 m/s or c = 3.00E8 m/s • Prac Pr 376

  8. Sources of Light • Luminous - emits light • Ex: sun, incandescent light bulb. • Illuminated - reflects light • Ex: moon • Luminous flux, P - rate at which light is emitted. • Unit is lumen, lm • Illuminance, E - illumination of a surface.

  9. Measurement of light depends on sensitivity of eye. • Candela, cd - measure of luminous intensity which is luminous flux that falls on 1 sq meter of sphere with one meter in radius. • Inverse Square 379 • Ex Prob 380 Prac Pr 381

  10. Inverse Square – varies inversely as square of its distance from a light source. • Fig 16-6 379 • Ex Prob 380 Prac Pr 381

  11. 16.2 Light and Matter • Transparent - transmit light waves • Translucent - transmit light waves but objects cannot be seen clearly. • Opaque - absorb or reflect light waves

  12. How We See • Light enters pupil & travels through lens. • Image is focused inverted (upside down) on retina. • Image is transferred to brain by optic nerve.

  13. Color • Red to violet • Spectrum - produced when white light is passed through spectrum. • Primary colors - red, green, & blue • Secondary - magenta, cyan, & yellow

  14. Complementary color - light of color & its complement add to produce white. • Dye - molecule that absorbs certain wavelengths & to transmit or reflect others.

  15. Pigment - larger than molecule. • Mix to form suspensions rather than solutions. • White light can be formed by adding together primary light colors, red, blue, & green.

  16. Subtractive primary colors, cyan, magenta, & yellow, are used in pigments & dyes to produce wide variety of colors.

  17. Colors in soap & oil films are caused by interference of specific colors of light reflected from front & back surfaces of thin film. • Light is polarized if only waves vibrating in particular plane are present.

  18. Fig 16-14 and 15 387 • Light is polarized by scattering in air. • Ray & wave models of light – Particle-Wave Duality of Light

  19. Conclusion • Light is a transverse wave that can be reflected, refracted, diffracted, transmitted, or absorbed. • Light travels through a vacuum. • Speed of light (c) is 3.00 x 108 m/s • Colors are produced additive or subtractive processes.

  20. Works Cited • Physics: Principles & Problems, Glencoe • http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html • http://acept.asu.edu/PiN/rdg/color/color.shtml • http://sln.fi.edu/color/color.html • http://imagers.gsfc.nasa.gov/ems/waves3.html. • http://www.glenbrook.k12.il.us/gbssci/phys/Class/waves/u10l1c.html • http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html • http://www.physicsclassroom.com/mmedia/optics/lr.html

  21. Transverse Wave

  22. Inverse Square Law

  23. Color Addition

  24. Reflection of Light

  25. Thin Film

  26. Thin Film Interference

  27. Polarizers

  28. Polarizers

  29. Polarizers

  30. Scattering

  31. Scattering

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