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Light: Geometric Optics. Introduction – 23-1, 23-4, 23-5, 24-10. Light. Electromagnetic Spectrum. Light. Light is the Part of the EM spectrum that stimulates the retina of the human eye ROY G BIV. Ray Model of Light. Light travels in straight line in vacuum or uniform media
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Light: Geometric Optics Introduction – 23-1, 23-4, 23-5, 24-10
Light • Electromagnetic Spectrum
Light • Light is the Part of the EM spectrum that stimulates the retina of the human eye • ROY G BIV
Ray Model of Light • Light travels in straight line in vacuum or uniform media • Ray model assumes straight line travel for light • Ray Optics – ray diagrams to study travel of light; ignores wave nature of light
Speed of Light • Before 1700, thought to be instantaneous • Galileo worked on speed of light • Couldn’t believe that it was that fast! • Ole Roemer – first to determine light traveled with measureable speed • A.A. Michelson – measured light between two mountaintops in California • 2.997996 x 108 +/- .00004 x 108 m/s • 1960’s Lasers found to measure speed of light better than atomic clocks v = λf = c
Sources of Light • luminous--body emits light • illuminated--body reflects light • incandescent--glows HOT; luminous; W wire is heated by electricity and glows inside a light bulb • luminous flux, P--rate at which light is emitted from a source • Lumen – lm – unit of flux • illuminance, E--lm/m2 or lux, lx
Illumination • 100W light bulb – 1750 lm • If 1m sphere: 1750 lm / (4π(1)2) = 1750/4π lx • If 2m sphere: 1750 lm / (4π(2)2) = 1750/16πlx • Candela cd – measures luminous intensity • 1750/4π lx = 139 cd
Illumination • To increase illumination • increase flux of alternate source • decrease distance between source and surface • Illuminance= E = P/4πd2 • perpendicular line between source and surface • point sources
Light and Matter • Transparent – light through; transmitted • Translucent — light sort of through; transmits and diffuses light • Opaque – light not through; absorbs reflects all light; no transmission
Color Models Additive - RGB Subtractive CMY