Electromagnetic Radiation The Nature of Light

The Human Eye  

Mixing Pigments (Subtractive) Magenta Cyan Yellow

Mixing Light (Additive) Green Red Blue

Human Eye Sensitivity to Color Violet Blue Green Yellow Orange Red

Stare at the Red Triangle

Stare at the Blue Triangle

Stare at the Green Triangle

Do you see a number?

Do you see a number? 45

Do you see a number? 6

Do You See a “2” or a “5”?

Color Blindness Test http://colorvisiontesting.com/ishihara.htm

Electromagnetic Spectrum

Examples Gamma rays (10-12 m) Visible light (4 x 10-7 m to 7 x 10-7 m) violet red Radio waves (104 m)

Wavelength (λ) and Frequency () Long Wavelength = Low Frequency Low Energy Short Wavelength = High Frequency High Energy

Wavelength and Frequency are Inversely Proportional; c =  c = 3.00 x 108 m/s (speed of light)  = wavelength, in meters.  = frequency in hertz (Hz or 1/s)

Calculate the frequency  = 6 x 10-7m  = 1 x 10-10m  = 1.5 x 10-18m  = 5.0 x 1014 Hz  = 3.0 x 1018 Hz  = 2.0 x 1026 Hz

Calculate the wavelength  = 1 x 108 Hz  = 1.2 x 1012 Hz  = 3 x 1027 Hz  = 3.0 m  = 2.5 x 10-4 m  = 1.0 x 10-19 m

Energy and Frequency are Directly Proportional; E = h E = energy in joules (J) per photon. h = Planck’s constant = 6.63x10-34 J•s  = frequency, in hertz (Hz or 1/s)

Calculate the energy  = 1 x 108 Hz 6.63 x 10-26 J  = 3.0 x 10-5 m ? ?

Calculating Energy per Photon Since c = λν and E = hν, then if follows that E = hc/λ Determine the energy per photon of an electromagnetic wave where λ= 3.0 x 10-5m E = (6.63 x 10-34 J•s)(3.0 x 108 m/s)/3.0 x 10-5m = 6.6 x10-21 J

Which has the longest wavelength? Green light or blue light? UV light or infrared? Green Infrared

Which possesses greater energy? Yellow light or orange light? X-rays or radio waves? Yellow X-Rays