Chapter 28: Color

Properties of white light Lights, Camera, Action Properties of white light Ex: sunlight Passed through a prism Refraction - Bending of light White light is combination of all colors VIB G YOR

Black is the absence of light Let’s Reflect Black is the absence of light objects appear black when they absorb light of all visible frequencies some reflection at the surface

Color is produced by absorption and reflection of light Let’s Reflect Color is produced by absorption and reflection of light Ex: a piece of red glass appears red because it absorbs all the colors that compose white light and transmits red Perceived color of an object is subjective and depends on the light source Light mix website

Colors by Transmission Pigments are materials that selectively absorb colored light electrons absorb certain frequencies light of other frequencies is reemitted from atom to atom/glass is warmed

Colors by Transmission Ex: window glass is colorless because it transmits light of all visible frequencies When red light shines on a red rose, why do the leaves become warmer than the petals? When green light shines on a red rose, why do the petals look black?

Sunny Days White light from the sun is composed of all visible frequencies Brightness of solar frequencies is uneven

Red, Green, and Blue are primary additive colors Let’s Mix It Up a Little Red, Green, and Blue are primary additive colors Red + Green + Blue = White Color Addition ex: Television Red + Green = Yellow Red + Blue = Magenta Green + Blue = Cyan http://www.usd.edu/coglab/rgb/a-colormix.html http://www.lon-capa.org/~mmp/applist/CYMColor/c.htm

Thanks for the Compliment Complementary Colors Two colors added together to form white Yellow + Blue = White Magenta + Green = White Cyan + Red = White Complementary color is the product when a color is subtracted from white light

Thanks for the Compliment Complementary color is the product when a color is subtracted from white light What color does white light minus yellow light appear? What color does white light minus green light appear?

Why… Is the sky blue? Are clouds white? Molecules in the air scatter light The tinier the particle, the higher the frequency of light that will scatter Our eyes are not sensitive to violet Are clouds white? Droplets that compose a cloud come in a variety of sizes This causes a variety of colors to be scattered

Why… Are sunsets Red? Low frequencies of light are scattered the least by nitrogen and oxygen molecules Red, Orange, and Yellow light are transmitted through atmosphere more readily than violet and blue Red light passes through the most atmosphere without interacting with matter

Why… Is water greenish blue? Red is absorbed by molecules in the water Complementary color is cyan

Every element emits different light patterns Spectroscopes What’s the Secret Code Every element emits different light patterns Spectroscopes Used to analyze light glowing from elements Form line spectrums

Blind spot in the eye – pg 474 Rods – Dim light receptors Eyes Blind spot in the eye – pg 474 Rods – Dim light receptors Cones – Color receptors 3 types, if one is not working - colorblindness Flag demo

Eyes

Eyes

Refraction Light is bent when it changes mediums Pencil in glass Looking at Fish Speed of light is less in all materials

Let’s Light It Up Refraction Due to time delay of absorption and reemission, speed of light is less red is the fastest http://mysite.verizon.net/vzeoacw1/rainbow.html blue is the slowest High frequency More interaction - absorption by the atoms takes time

Reason for Refraction Road/Mud analogy Shortest Distance If one wheel hits the mud the car turns that direction Shortest Distance Light prefers the shortest path

Lenses – focus or spread light Uses of Refraction Lenses – focus or spread light Convergent Divergent

Eyeglasses and how they work