Light! Electromagnetic Waves: are vibrations of the electric and magnetic fields of moving charged particles. Electromagnetic Spectrum: is the complete range of possible e-mag wave frequencies: Radio, Microwave, IR, Visible, UV, X-ray, Gamma ray. Really Murderous Inmate, Roy G Biv, Used X-ray Guns! Our eyes are only able to see E-mag waves in a small range: 620 – 380 nm. This is called visible light which can be seen in order in rainbows. (Red is low energy long λ, violet is high energy, short λ) All E-mag waves travel at the same speed in a vacuum, no matter their λ or f m/s. This speed slows when light travels through matter, and depends on density. 1) The lowest energy E-mag waves have a very long ___ and a low _____ and are classified as ____ waves. What is the λ of a radio wave with a frequency of 9.5E8 Hz? 2) The highest energy E-mag waves are called _____ _____ and come from radioactive material. They have a very ____ ____ and a very ___ ____. What is the frequency of a gamma wave with a λ of 5E - 12 m? 3)______ is the color with the least energy. It has a λ of ~ 700 nm. What is the frequency of this light? 4) How far do microwaves travel through the vacuum of space in 5 minutes? How do we see? The only thing our eyes see is _____. A light source radiates visible light, which strikes objects. Some wavelengths are absorbed (b/c the energy of that λ is perfectly sized to vibrate the molecules) but some are _______ off and back to our eyes. White objects: do not ______ any colors. All are reflected; that’s why white is so bright/blinding- lots of energy Black objects: absorb ___ ______; none are reflected. That’s why they get so hot. Newton (of Newton’s 3 laws fame) was the 1 st person to realize that white light is composed of all the rainbow colors. He used a glass _____ to split light into its colors – this is called light ________. Light dispersion happens naturally when white sunlight is dispersed in rain drops in the sky. It’s a ________! Why? Remember light’s speed changes when it travels into a different density medium (air to glass, then glass to air) This speed change is called ______. High f light (violet) slows down more than low f (red) light. B/c this change happens at an angle in a prism, all the λ’s are spread out in order.

Color and Polarization Primary and Secondary Light Colors The three primary light colors (___, ____ and ____) when mixed together create the secondary light colors. Red + Blue = ________ Blue + Green = _______ Red + Green = ________ Red + Blue + Green =________ Secondary colors are two primary colors mixed together. If you add the 3 rd color it makes white. The 3 rd color is called the _______ color. Magenta + _______ = white Cyan + _______ = white Yellow + _______ = white Light Colors vs. Pigment Colors Colors of Pigment: (Paint, crayons etc.) You learned as a child that you can mix red yellow and blue to make other colors. Actually, _____, _______ and ______ are the 3 best colors to mix. They can be mixed to make any color. (Think of the ink colors in a color printer. Look at the edges of colored book illustrations. ) Color ‘Tiles”: we draw these boxes to figure out what color we see when a pigment absorbs or reflect a light color. Ex: What color do we see when yellow light strikes a magenta pigment? Polarization: Light is a transverse wave, but not all the waves wiggle in the same plane. Waves can wiggle or. There are filters made of translucent plastic that filter out light except in one plane. These are called ________ filters. Lasers: are simply ________ light: Light of one color (one λ) that is all in phase and vibrates in the same plane (polarized). Caused by electrons in noble gases falling back down from a high energy level to a lower one. Incoherent light with many λ incoherent light of one λ coherent light = laser light Primary Colors of Light: Our eyes do not see every individual color, but only the averages of the low, medium and high wavelengths, which are: ____, _____, and ____. The 3 main light colors combine to create white light just as a spectrum does. What color would we see if cyan light shone on a mix of magenta and green pigment? What color would we see if red light shone on blue pigment? What color would we see if white light shone on red pigment? What color would we see if yellow light shone on a mix of cyan and yellow pigment? Sunglasses reduce “glare” from roads and snow and water by blocking horizontally reflected light from smooth surfaces. Easier driving!