Concave Mirrors

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Concave Mirrors
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Taken in a place with no name (See more photos or
videos here)
"Have you ever approached a giant concave mirror?
See your upside-down image suspended in mid-air.
Walk through the image to see a new reflection,
right-side-up and greatly magnified. In the
background you see reflected a room full of
visitors enjoying other

• Curves inward

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Concave Mirrors

• AKA converging mirror
• Described as a mirror with a surface that
  curved inward like a bowl

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Terminology
Centre of Curvature (C)
Vertex
Principle Axis (PA)
Focus (F)
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Light Rays in a Concave Mirror

• Purpose To determine how light behaves in a
  concave mirror
• Observations

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Rules for Concave Mirrors Lab

• Outline mirror in book, and label Principle axis.
• Shine light bulb of ray box at mirror. You should
  notice all the rays focus on 1 point (the focus).
  Mark and label this point F.
• Measure the distance from the mirror to point F.
  Use this distance to mark C, a point on the other
  side of F.
• Shine a single light ray through F at mirror.
  Copy the light beam path.
• Shine a light ray parallel to the P.A. Copy the
  light beam path.
• Shine a light ray through C. Copy the light beam
  path.
• Shine a light hitting the vertex. Copy the light
  beam.

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• Analysis
• What happens when you shine a light ray through
  the focus (F)?
• What happens when you shine a light ray parallel
  to the principle axis (PA)?
• What happens when you shine a light ray through
  the centre of curvature (C)?
• What happens when you shine a light ray at the
  vertex (V)?

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Light Ray Rules for Concave Mirrors

1. A light ray parallel to P.A. reflects through F.
2. A light ray that passes through F will reflect
   parallel to P.A.
3. A light ray hitting the vertex (perpendicular to
   P.A.) will follow ?i ?r reflection rule.

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Using Light Ray Rules to Find an Image

• Case 1 An object outside C
• Case 2 An object between C and F
• Case 3 An object on F
• Case 4 An object between F and Mirror

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Locating Images in Curved Mirrorswith Lab Benches
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Concave Mirror Applications

• A searchlight/car headlight
• radiates light rays from focus to reflect rays
  parallel (beam of light)
• Satellite Dish
• TV dish receives parallel rays and reflects them
  to focus where wave detector is
• Cosmetic Mirrors
• - Large virtual images provide magnified face

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• Worksheet