Wave Nature of Light

 1. What property of light determines the color?  2. T F The color white is the presence of all colors?  3. What are the 3 primary colors?  4. What are the 3 primary pigments?  5. What happens if I put 2 polarizing filters at 90 degrees to each other?

 Last section we discussed the ray nature of light and how we came up with the speed of lightspeed  1665 Grimaldi showed that the shadows left by light are not perfectly sharp ◦ Explained this as the diffraction of light or the bending of light as it passes through openings  Huygens finally gave support to diffraction of light by explaining the bending of light through openings  1666 Newton performed experiments on the color of light by passing a narrow strip of sunlight through a prism to separate colors of light

 Was finally accepted that it is the wavelength of the light that causes it to diffract at different amounts ◦ Thus the visible light that we see is from wavelengths of 400nm (violet) to 700 nm (red)

 There are 3 primary colors of light which are red, green, and blue.  If we add any 2 primary color we get the secondary colors magenta, cyan, and yellow Primary colors are defined as any 2 colors that can be combined to make white light.

 There are materials such as dyes and pigments that naturally absorb certain colors of light  Main difference between the 2 is that pigments are usually made of minerals and dyes are usually plant or insect based.

 Pigments that only absorb 1 color of light is called a primary pigment. The 3 primary pigments are yellow, magenta and cyan  Secondary pigments then absorb 2 colors of light and are thus red green and blue

 Polarization of light relates to the filtering out of wavelengths based on orientation ◦ They only allow 1 orientation to go through  Thus if you place 2 polarized lenses at 90 degrees you block out all light

 Like sound light also undergoes the doppler shift. ◦ Unlike sound, the V is much less than C so we can simplify the equation as follows  F obs = f( 1 +/- v/c)  Since most of the doppler shift of light was analyzed by astronomers, they were interested in wavelength instead of frequency  Thus the equation is as follows  (λ obs – λ ) = Δλ = +/- v/c λ