Mirror mirror on the wall

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Mirror mirror on the wall

• Chapter 29
• Reflection and Mirrors

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I. Reflection

• A. The bouncing back of a particle or wave that
  strikes the boundary between two substances
• 1. How they bounce back depends on the surface
  they hit

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• 2. Spring analogy
• Wave is totally reflected when it reaches a
  completely rigid boundary

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• 2. Spring analogy
• Wave is totally reflected when it reaches a
  completely rigid boundary
• Partially reflected if less rigid
• Some energy reflected back
• Some transmitted into new media
• DEMO with spring

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• B. Metal surfaces are rigid to light waves
• So almost total reflection

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• B. Metal surfaces are rigid to light waves
• So almost total reflection
• C. Other materials are less rigid
• So partial reflection

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II. The Law of Reflection
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II. The Law of Reflection
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• B. Angle of incidence equals the angle of
  reflection
• C. Applies to partially reflected and totally
  reflected wave
• Also works in billiards for all you pool sharks
  out there

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So. What is the light doing?
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Line of sight

• In order to view an object, you must sight along
  a line at that object and when you do light will
  come from that object to your eye along the line
  of sight.

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• In order to view an image of an object in a
  mirror a person must sight along a line at the
  image of the object.

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So why do we see an image?

• image animation

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III. Flat Plane Mirror Images

• A. Example Rays leave from the arrow and reflect
  from mirror to eye

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• B. Rays diverge from tip of object and reflect
  from mirror to eye
• C. To your eye light appears to come from behind
  the mirror
• virtual image

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• D. The image is as far behind the mirror as the
  object is in front of it
• E. The image and object are the same size.

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IV. Ray Diagrams

• A. Diagram which traces the path which light
  takes in order for a person to view a point on
  the image of an object.
• You will draw some on the worksheet.

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Concept quiz

• A person stands 2 m in front of the mirror. How
  far is she from her image?
• 1. 2 m
• 2. 4 m
• 3. 6 m
• 4. 1 m