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Light. Illumination. Ray Model of Light-travels in a straight path, can only be changed by placing an obstruction Luminous =Sun Illuminated = Moon Opaque Transparent Translucent. Quanity. Luminous Flux (P)-Unit- LUMEN (lm) Rate at which light is emitted from a luminous source
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Illumination • Ray Model of Light-travels in a straight path, can only be changed by placing an obstruction • Luminous =Sun • Illuminated = Moon • Opaque • Transparent • Translucent
Quanity • Luminous Flux (P)-Unit- LUMEN (lm) • Rate at which light is emitted from a luminous source • Illuminance (E)- Unit-LUX (lx) • illumination of a surface or the rate at which light strikes the surface • Luminance Intensity- Unit: Candela (cd) • Luminous flux that falls on 1 m2 • E=P/4 pi r2
Practice Problem • What is the illuminance on your desktop if it is lighted by 1750 lm lamp that is 2.5 m above your desk? 22.3 lx • A public school law requires a minimum illuminance of 160 lx at the surface of each student’s desk. An architect’s specifications call for classroom lights to be located 2.0 m above the desks. What is the miniumum luminous flux that the lights must provide? 8042 lm
Remember Waves! • Diffraction
Polarization • Production of light in a single plane of oscillation • Only parallel can pass through