Class Starter 1. How does the amount of energy in the electromagnetic spectrum change as you travel from radio waves to gamma rays? 2. Besides cooking, name one other use for microwaves.

Light Properties Speed of light is ~ 300,000,000 m/s (671 million mph) It takes about 8 minutes for light to travel from the sun to Earth. Light can travel around the Earth 7 times in 1 second.

Light & Matter 1. Opaque Materials –Do not allow light to pass through –They either absorb or reflect light. –Ex. Aluminum foil

Light & Matter 2. Translucent Materials –Allow some light to pass through, but will distort (bend) image. –Ex. Privacy glass,wax paper

Light & Matter 3. Transparent Materials –Allow almost all light to pass through without distorting. –Ex. clear glass

Refraction of Light Bending of light waves due to medium. The more dense the medium the slower the light waves. –Ex. Prisms, Glass, Water

Types of Light 1. Incandescent –Heats a filament (made of tungsten) until it glows. –Cheap –Don’t last long –Ex. Typical light bulb

Types of Light 2. Fluorescent –Glowing phosphorus –Use less energy –Last longer –Used in schools, hospitals, offices

Types of Light 3. Neon –Contains noble gases –Used in signs

Types of Light 4. Sodium Vapor –Contains neon and sodium metal –Gives the light a yellow tint –Used in street lights

Types of Light 5. Halogen –Contains fluorine and chlorine gases –More expensive –Long life span –Bright –Bluish tint –Used in headlight and lamps

Types of Light 6. Laser –Beam of electrons –Used in medicine & entertainment (CD/DVD players)

Using Light 1. Filters  UV rays, colors –Ex. Sunglasses, stained glass

Using Light 2. Holograms  3D image created by refracting light. –Ex. toys, driver’s license

Using Light 3. Optics  Tiny glass tubes that carry light –Ex. toys, communication, medical

Color from Light An object is “colored” because of the light it reflects – all other colors are absorbed. –Ex. An apple appears red because it reflects red light.

Color from Light White light contains all the possible color variations. We are capable of seeing color because of color- sensitive cells in our eyes called rods and cones.

Color from Light Rods allow us to see brightness of light. Cones allow us to see actual color. The number of rods and cones in an individual eye’s varies from person to person.

Color Coding: The Color Wheel The primary colors of light are red, blue, and green. Red Green Blue

Color Coding: The Color Wheel Color Addition: combining primary colors of light to produce secondary colors of light. –Red + Green  Yellow –Red + Blue  Magenta –Blue + Green  Cyan

Color Coding: The Color Wheel