Formation of Images by Spherical Mirrors

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Formation of Images by Spherical Mirrors
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For an object infinitely far away (the sun or
starts), the rays would be precisely parallel.
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If a mirror is small compared to its radius of
curvature, so that the reflected rays make only a
small angle upon reflection, then the rays will
cross each other at a single point, or focus.
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The principal axis of a mirror is defined as the
straight line perpendicular to the curved surface
at its center.
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The point F, where the rays parallel to the
principal axis, come to a focus, is called the
focal point of the mirror.
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The distance between focal point and the center
of the mirror is called the focal length, f, of
the mirror.
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Another way of defining the focal point is to say
that it is the image point for an object
infinitely far away along the principal axis.
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Finding the Image Position for a Curved Mirror
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• ray 1 is drawn parallel to the axis therefore it
  must pass along a line through F
• ray 2 is drawn through F, as result is must
  reflect into parallel to the principal axis ray
• ray 3 is chosen to be perpendicular to the
  mirror, and so is drawn so that it passes through
  C, the center of curvature it will be reflected
  back on itself.

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Mirror Equation
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The lateral magnification, m, of a mirror is
defined as the height of the image divided by the
height of the object
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The Sign Convention

• the image height hi is positive if the image is
  upright, and negative if inverted, relative to
  the object
• di and do are both positive if image and object
  are on the reflecting side of mirror, but if
  either image or object are behind the mirror, the
  corresponding distance is negative.