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Everybody Loves Ray Diagrams

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Center of curvature: The point in the center of sphere from which ... Process for Concave RDs. Pick a point on the top of the object and draw two incident rays. ... – PowerPoint PPT presentation

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Title: Everybody Loves Ray Diagrams


1
Everybody Loves Ray Diagrams!
2
Why Ray, Why?
  • We draw ray diagrams to determine
  • Location
  • Size
  • Orientation
  • Type
  • of images formed by a concave or convex (think
    curved) mirror.

3
Key Terms!
  • Center of curvature The point in the center of
    sphere from which a curved mirror was sliced.
  • Principal Axis The line passing through the
    center of the sphere, attached to the mirror in
    the exact center.
  • Vertex The geometric center of the mirror.
  • Focal Point Midway between the vertex and the
    center of curvature. Its also the point at which
    light traveling parallel to the principal axis
    will meet after reflection.

4
Picture, Please!
Vertex
Focal Point
Center of Curvature
5
Rules for Concave Mirrors
  • Any incident ray traveling parallel to the
    principal axis on the way to the mirror will pass
    through the focal point when its reflected.
  • Any incident ray passing through the focal point
    on the way to the mirror will travel parallel to
    the principal axis when its reflected.

6
Ok, Pictures Quickly!
Rays are parallel to the principal axis on the
way in, so they go through the focal point when
reflected.
Rays go through the focal point on the way in, so
they are parallel to the principal axis when
reflected.
7
This is How We See!
  • But dont worry well start with simplified
    drawings!

8
Process for Concave RDs
  • Pick a point on the top of the object and draw
    two incident rays.
  • Draw one ray passing through the focal point
  • Draw the second parallel to the principal axis.

9
Keep Going
  • Reflect the IRs so the ray passing through the
    focal point reflects parallel to the principal
    axis.
  • Reflect the ray which traveled parallel to the
    principal back through the focal point.

10
Almost Done!
  • Mark the image of the top of the object.
  • Repeat the process for the bottom of the
    object.
  • Draw a line from the top of the image to
    principal axis. (the bottom of the reflected
    image will always fall on the principal axis)

11
So Lets Recap!
  • The image depends on the distance of the object
    from the mirror.
  • You have these choices
  • Outside the center of curvature (C)
  • At the center of curvature (C)
  • Between the center of curvature (C) and the
    focus (F)
  • Between the focus (F) and the mirror (this
    ones a bit different, so be patient)

12
Outside the center of curvature (C)
13
At the center of curvature (C)
14
Between center of curvature (C) and the focus (F)
15
So Why Did We Do This?
  • In these three cases 1) object located beyond C,
    2) object located at C,and 3) object located
    between C and F - light rays converge to a point
    after reflecting off the mirror. In such cases, a
    real image is formed.
  • A real image is formed whenever reflected light
    passes through the image location. Unlike plane
    mirrors which always produce virtual images,
    concave mirrors can produce real and virtual
    images! (Cool, huh?)

16
When do Concave Mirrors Make Virtual Images?
  • A virtual image is formed if the object is
    located less than one focal length from the
    concave mirror.
  • Take a look!

17
Between the focus (F) and the mirror
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