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Light, Polarization & Color
The nature of an object’s color
• What are examples of color?
• How can we tell one shade of a color from another?
• Do objects seem to sometimes change color under different light conditions?
White Light
Def: light given off from a source that emits all colors of light at once.
Light from a light bulb isn’t just one color, it’s three!
Primary Colors
• There are only three primary colors:
• Red, Green, and Blue
• ALL other colors can be made by mixing these together.
Complimentary Colors
• Mixing two primary color together makes one of the complimentary colors:
• Red + Green = Yellow
• Green + Blue = Cyan
• Blue + Red = Magenta
The Color White
• If you mix all three primary colors together, they will appear to be the color white.
• There are an infinite number of color combinations of Red, Green, and Blue to create different “recipes” of color.
Overlapping Colors Of Light
Creating the rainbow…
• Smoothing out the colors would make the diagram look something like this.
What’s different about colors?• Each color of light has it’s own specific
wavelength.
So….
• If every color has a different wavelength, maybe they behave differently when different colors of light hit the same object.
• This is what gives an object it’s color.• (At least, what we think it’s color is)
Everything’s a Mirror
• Almost all objects reflect some kinds of light and absorb other kinds.
• White objects reflect all colors of light.
• Black objects absorb all colors of light.
• Absorbing light transfers energy to an object, so black objects heat up more rapidly than white objects.
Everything’s a Mirror
• Objects in between only reflect certain kinds of light.
• Example: Green leaves reflect green light, but absorb all other colors of the rainbow.
When’s a White shirt not white?
• A white tee shirt reflects all colors of light, making it appear white.
• If you look at a white shirt under red light, it looks red, because it’s reflecting all the light that’s there (only red), so that’s what you see.
Light Waves
• Since light travels in waves, they would look like this from the side:
• But this from the front
Light in the real world
• Looking at a beam of light from the front, individual waves might look like this:
Polarizing Lens
• A polarizing lens only allows light waves lined up in a certain direction to pass through.
• A lens looks like the boards on a deck:
Polarizing Lens
• Only light that will “fit between the cracks” will pass through the lens. All the other light waves bounce off.
• Only these three ray will pass through
Uses of Polarized Light
• Polarizing Lenses can be used in the lab in experiments, but practical applications are:
• Sunglasses• Window Tint• Video Cameras• Binoculars/ Telescopes
• Using Polarizing lenses helps reduce glare and increase visibility in optics applications.
Practice
• To practice with these concepts, complete the Section Review on Pg. 474 #1-4.