The Vibrating String

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The Ray Box Part Two
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Law of Refraction

• The law of refraction for light states that a
  light ray is bent away from its original
  direction when it passes from one medium to
  another if it strikes the interface between the
  two media at a nonzero angle of incidence.

qi
Incident Beam
Air
Glass
Refracted Beam
qR
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• Refraction is the reason why swimming pools look
  more shallow than they really are.
• Refraction is the property that explains the
  operation of telescopes, binoculars, eyeglass
  lenses, projector lenses, etc.

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When light passes from one medium into another,
part of the light is transmitted into the next
medium and part of the light is reflected back
into the first medium. To show this look at the
white light below that is incident upon a red
filter.
There would be multiple reflections inside the
filter, but they would become weaker with each
reflection.
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Types of Lenses
Double Convex
Double Concave
Concave Meniscus
Plano Convex
Plano Concave
Convex Meniscus
Farsighted people use lenses similar to these.
Nearsighted people use lenses similar to these.
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Types of Lenses
Double Convex
Double Concave
Concave Meniscus
Plano Convex
Plano Concave
Convex Meniscus
Convex lenses are thicker in the center
than they are at the edges.
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Types of Lenses
Double Convex
Double Concave
Concave Meniscus
Plano Convex
Plano Concave
Convex Meniscus
Convex lenses converge light rays concave lenses
diverge light rays.
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A Convex Lens Converges Light Rays
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A Concave Lens Diverges Light Rays
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Color Addition
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• Through color addition you are able to see a wide
  range of colors from a color TV or color
  projector which actually only emit three
  different colors.
• These colors are red, green, and blue.
• They are called the additive primaries.
• Your vision system adds these together to see a
  single color from a single location illuminated
  by more than one color.
• You can even see colors that dont appear in the
  continuous emission spectrum of the sun.
• Red, green, and blue are used as the additive
  primaries because this set of three will produce
  the widest range of colors that you visually
  experience.

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• On the next slide you will see what happens as
  you add colors to produce other colors.

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Colors in White
White
Red
Green
Blue
You can see that these three add to give white.
Yellow
Note that yellow is the addition of red and green.
Cyan
Magenta
Note that cyan is the addition of green and blue.

Note that magenta is the addition of red and blue.
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To summarize, see color addition circles on next
slide.
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Color Addition Circles
What you are about to see is what you would get
with three partially overlapping spotlights
reflecting off a white screen.
Yellow
Yellow
Red
Red
Green
Green
Cyan
Cyan
Magenta
Magenta
Blue
Blue
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Color Subtraction
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• Through color subtraction you are able to see a
  variety of colors from printings, paintings, etc.
• If you have ever bought printer inks, you will
  notice that the ones used to provide a variety of
  colors in printing are yellow, cyan, and magenta.
• They are called the subtractive primaries.
• In subtraction, colors are eliminated by the
  absorption of colors that were in the original
  illuminating source.
• This particular set of three colors, yellow,
  cyan, and magenta, will produce the widest range
  of colors that you visually experience.

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• On the next slide you will see what happens as
  you remove different colors from white light.

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Colors in White
You get blue.
Take away yellow and what is left?
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Colors in White
You get red.
Take away cyan and what is left?
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Colors in White
You get green.
Take away magenta and what is left?
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To summarize, see color subtraction circles on
next slide.
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Color Subtraction Circles
What you are about to see is what you would get
with three partially overlapping transparencies
on an overhead projector.
Green
Green
Cyan
Cyan
Yellow
Yellow
Blue
Red
Red
Blue
Magenta
Magenta
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Complementary Colors

• Any two colors that add to give white are said to
  be complementary colors.
• Of the primary colors, both additive and
  subtractive, the following pairs are
  complementary colors.
• Red and Cyan
• Green and Magenta
• Blue and Yellow

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• When complementary colors are used in color
  subtraction, generally black is produced.
• One exception will show this in the demonstration
  that follows.
• Your laboratory assistant will now demonstrate
  color subtraction using only complementary colors.

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• On the next slide you will see what happens as
  white light passes through the blue and yellow
  filters.

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A yellow filter lets this through.
A blue filter lets this through.
It is obvious that green will get through both
filters.
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• This situation only occurs with this particular
  combination of filters.
• It is because filters pass a range of colors
• and in this case with blue and yellow,
• the ranges overlap because blue and yellow are
  fairly close to each other in the color spectrum.