LightLight

The Electromagnetic The Electromagnetic SpectrumSpectrum

◦ Long to short Radio Microwave Infrared Visible light Ultraviolet X-ray Gamma ray

◦ High frequency to low Gamma Ray X-Ray Ultraviolet Visible light Infrared Microwave Radio

Visible SpectrumVisible Spectrum Long to short

◦ Red

◦ Orange

◦ Yellow

◦ Green

◦ Blue

◦ Violet

High frequency to low◦ Violet

◦ Blue

◦ Green

◦ Yellow

◦ Orange

◦ Red

Color AdditionColor AdditionThree primary colors: Red,

Green, BlueRed + Green = YellowGreen + Blue = CyanBlue + Red = MagentaRed + Green + Blue = White

Speed, Frequency & Speed, Frequency & WavelengthWavelengthIn meters/second:c = 3.0 x 108 m/sLike other waves, c = fλ

Frequency, Wavelength & Frequency, Wavelength & ColorColor1 nm = 1 nanometer = 10-9 m = one billionth of a

meter

color wavelength

red ~ 700–635 nm

orange ~ 635–590 nm

yellow ~ 590–560 nm

green ~ 560–490 nm

blue ~ 490–450 nm

violet ~ 450–400 nm

Light IntensityLight IntensityThe standard unit of light output is the

lumen (lm)The standard unit of light intensity is the

lux (lx)1 lx = 1 lm/m2

I ~ 1/r2