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 California2.997996 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 sourceLumen – 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) = 1750/16π lx

Candela cd – measures luminous intensity1750/4π lx = 139 cd

Illumination To increase illumination

increase flux of alternate sourcedecrease 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

Polarizers

Dual Polarizers