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Light

Chapter 16. Light. Light. The Ray Model of Light was introduced as a way to study how light interacts with matter Ray= a straight line that represents the linear path of a narrow bean of light Rays can change direction if reflected or refracted. Light Sources.

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Light

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  1. Chapter 16

    Light

  2. Light The Ray Model of Light was introduced as a way to study how light interacts with matter Ray= a straight line that represents the linear path of a narrow bean of light Rays can change direction if reflected or refracted
  3. Light Sources There are MANY different sources of light but there are only two TYPES of sources 1. Luminous Source = an object that emits light (such as the sun or a candle) 2. Illuminated Source = object that becomes visible as a result of the light reflecting off it (such as the Moon)
  4. Properties of Light The illuminance produced by a point source is proportional to 1/r2 (the inverse square law)
  5. More “Stuff” Speed of Light (c) = 3.00 x 108 m/s Diffraction = the bending of light around a barrier
  6. Electromagnetic Spectrum As the wavelength of visible light decreases, the color changes from red to violet As wavelength decreases, the frequency increases, and the energy of the wave increases
  7. Electromagnetic Spectrum
  8. Primary Colors of Light Primary colors of light = red, green, and blue Secondary colors=yellow, cyan, and magenta
  9. Color Complementary colors = 2 colors of light that can be combined to make white light Objects appear a certain color because they reflect that color light and absorb all the others
  10. Polarization Polarization is the production of light in a single plane of oscillation
  11. Seeing Light Doppler Shift= the difference between the observed wavelength of light and the actual wavelength ∆λ=(λobs- λ)=+/- (v/c) λ
  12. Doppler Shift A positive change in λ = red shift The relative velocity of the source is away from the observer A negative change in λ = blue shift The relative velocity of the source is towards the observer
  13. Doppler Shift Stellar motion take the spectrum of a star compare observed wavelengths of absorption lines to lab values (H, Fe, Na, etc.) calculate star’s radial motion (need distance and tangential angular motion to get space motion) NO, you won’t have to calculate this!!!
  14. Chapter 17

    Mirrors

  15. Videos Light, Lenses, and Lasers Telescopes Archimedes Death Ray
  16. Reflection Reflection is the change in direction of a wave at an interface between two different media so that the wave returns into the medium from which it originated. Law of reflection: the angle of reflection=the angle of incidence θr=θi
  17. Reflection Specular reflection = when light hits a smooth surface the rays are reflected in parallel Diffuse reflection = when light hits a surface that is rough (on the level of the wavelength of light) the light scatters
  18. Reflection Reflected rays of light that enter the eye appear to originate at a point behind the mirror Virtual image= a type of image formed by diverging light rays Always on the opposite side of the mirror from the object
  19. Chapter 18

    Refraction and Lenses

  20. Refraction Refraction= the bending of light as it passes into a new medium
  21. Refraction Index of Refraction= the ratio of the speed of light in a vacuum to the speed of light in that medium The index of refraction determines how much the light bends/refracts n=c/v
  22. Total Internal Reflection Phenomenon that occurs when light traveling from a region of a higher index of refraction to a region of lower index of refraction strikes the boundary at an angle greater than the critical angle such that all light reflects back into the region of higher index Critical angle = the angle of incidence above which total internal reflection occurs
  23. Total Internal Reflection
  24. Chapter 19

    Interference and Diffraction

  25. Interference Incoherent light = light with unsynchronized wave fronts that illuminates objects with an even, white light EX: the light you see when you look at objects illuminated by a light bulb Coherent light= light from two or more sources that add together in superposition to produce smooth wave fronts
  26. Interference Interference fringes = a pattern of light and dark bands on a screen, resulting from the constructive and destructive interference of light waves passing through two narrow, closely spaced slits in a barrier
  27. Interference Thin-film interference : a phenomenon in which a spectrum of colors is produced die to the constructive and destructive interference of light waves reflected in a thin film
  28. Diffraction The phenomenon of diffraction involves the spreading out of waves past openings which are on the order of the wavelength of the wave Diffraction pattern : a pattern on a screen of constructive and destructive interference of Huygens’ wavelets
  29. Diffraction Diffraction Grating = a device made up of many single slits that diffract light and form a diffraction pattern that is an overlap of single-slit diffraction patterns The tracks of a compact disc act as a diffraction grating, producing a separation of the colors of white light.
  30. Color Puzzles WOOT!
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