Optics

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Optics
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What is Optics?

• the study of how light behaves, or
• the collection and use of light to create images.
• Optical system Collects light and uses
  refraction and reflection to form an image
• lenses-which refract (bend) light
• mirrors - which reflect (bounce) light

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How can it bend?

• Light always travels in a straight line, but if
  it encounters another object or medium, it can
  change directions.
• when light is bent so that it comes together it
  is called converging
• when light is bent so that it spreads apart it is
  called diverging

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Light Rays

• an imaginary arrow that follows a single beam of
  light

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Bending of light that occurs when light crosses a
boundary between two different substances.
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Objects or waves bounce off a surface
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Images

• A place where many light rays from the same point
  on an object meet together again in a point
  called the focus, or focal point.
• They are pictures of objects
• Two types of images
• virtual - "not real" - the image only seems to be
  where it is cannot be projected onto a screen
• real -can be projected onto a screen, because the
  light actually passes through the point where the
  image appears

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Optical Devices

• Most optical devices have two functions
• 1. They collect light rays
• 2. They bend the collected rays to form an
  image.
• To illustrate how an optical device works, we
  draw ray diagrams to trace several light rays
  through a system

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The Ray Diagram
Two rules 1. In through the focal point, out
parallel
2. In parallel, out through the focal point.
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Ray diagrams

• Help answer questions like
• Where is the focal point (or is there one)?
• Will the image be magnified or reduced in size?
• Will the image be upside down or right side up?
• Will the image be inverted left or right?

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Law of Reflection
Light rays bounce off a mirror at the same angle
at which they arrive.
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Three Types of Mirrors

• plane - flat
• image is right-side-up, the same size and
  virtual
• concave - curved inward creates a focal point
• if the object is placed at the focal point, the
  image is inverted, smaller, and real
• if the object is placed closer to the mirror the
  image is larger and virtual
• convex - curved outward
• the image is right-side-up, smaller, and virtual
• objects appear farther away than they actually are

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Lenses

• a transparent material that refracts light
• usually made of glass or plastic with one or two
  curved surfaces

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Bending of light that occurs when light crosses a
boundary between two different substances.
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Two types of lenses

• convex converging
• - thicker in the center than at the edges
• converges the light rays (forms a focal point)
• forms a real image (magnifies objects)
• corrects farsightedness
• concave diverging
• thicker at the edges and thinner in the center
• diverges the light rays
• images are smaller and right-side-up
• forms virtual images
• corrects nearsightedness

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