Refraction and Lenses

1
Refraction and Lenses

• Refraction the change in direction when light
  enters a material with a different speed of light
• Light slows down when in glass vs. air.
• Light changes direction when it enters the glass
  and slows down.
• It changes direction when it leaves the glass and
  speeds up again.

2
Why does it change direction?
Waves move slower in a more dense medium than
in a less dense medium and vice versa.
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Concave vs. Convex
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Lenses

• Convex or converging lenses (like a magnifying
  glass) direct light inward or focus light to a
  point
• Concave or diverging lenses direct light outward

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Far vs. Nearsightedness

• Farsightedness. Light rays entering the eye
  particularly from nearby objects will not be
  brought to a focus by the time they strike the
  retina. Far away objects can be seen more easily.
  Farsightedness is called hypermetropia.
• Nearsightedness. The image of distant objects is
  brought to a focus in front of the retina and is
  out of focus again before the light strikes the
  retina. Nearby objects can be seen more easily.
  Nearsightedness is called myopia.

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What it looks like

• Farsightedness focuses behind retina need a
  convex lens to correct
• Nearsightedness focuses in front of the retina
  need a concave lens to correct

7
Other interesting light stuff

• Total internal reflection
• Cool prism demos
• Optical fiber demo and use
• Total internal reflection and refraction
• RAINBOWS
• Double rainbows
• Polarized Filters
• Sunglasses
• Window tint