Atmospheric Refraction

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1. What is the fundamental difference between a real
   image and a virtual one?
2. Parallel light rays are focused on the focal
   point of a concave mirror. Where do you want to
   place the bulb in a searchlight, which uses a
   concave mirror , to produce a parallel beam?

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Atmospheric Refraction
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Dispersion and Colors
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One combination of light beams that produces most
of the colors that we perceive is red, green and
blue. These are primary colors.
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Red Green Yellow
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Blue Green Cyan
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Red Blue Magenta
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Two colors that produce white light when added
together are called complementary colors.
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Mixing Paints and Mixing Colored Lights
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Mixing paints is different from mixing colored
lights. Mixing paints is subtractive process,
whereas with light beams you are adding colors.
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Why is the sky blue? Why is the sun yellow?
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1. What color is produced by the overlap of a blue
   spotlight and a red spotlight?
2. A surface appear yellow under the white light.
   How it will appear under red light? Under green
   light? Under blue light?
3. A substance is known to reflect red and blue
   light. What color would it have when it is
   illuminated by white light? By red light?
4. If you remove all of the green light from white
   light, what color would you see?

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Rainbows
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Thin Lenses
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Any lens that is thicker in the center than at
the edges will make parallel rays converge to a
point and is called a converging lens. Lenses
that are thinner in the center than at the edges
are called diverging lenses because they make
parallel light diverge.
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Lenses in eyeglasses are made with one convex
surface and one concave surface. How can you tell
if the lenses are converging or diverging?
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Finding the Image Position Formed by a Thin Lens
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• ray 1 is drawn parallel to the axis therefore it
  is refracted by the lens so that is passes along
  a line through the focal point
• ray 2 is drawn on a line passing the other focal
  point F and emerges from the parallel to the
  axis
• ray 3 is directed toward the very center of the
  lens, this ray emerges from the lens at the same
  angle as it entered.

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The Lens Equation
Converging Lens
Diverging Lens
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1. The focal length is positive for converging lens
   and negative for diverging.
2. The object distance is positive if it is on the
   opposite side of the lens from where the light is
   coming otherwise it is negative.
3. The image distance is positive if it is on the
   opposite side of the lens from where light is
   coming.
4. The height of the image is positive if the image
   is upright and negative if the image is inverted
   relative to the object.

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Lateral Magnification