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Convex Mirror Images

Object standing by a convex mirror.

What about the other side of the spoon, convex mirrors? The figure shows an object standing in front of a convex mirror. The procedure here will follow the two Light Ray Diagram rules that we have employed previously.

    Ray Diagram Rules
  1. Draw two light rays.
  2. Choose the easiest two!
Ray from object top to mirror and optic axis intersection.

To draw the first light ray, start at the top of the object. Draw a straight line to middle of the mirror. Sketch the outgoing ray using the principle that the incident reflection angles are equal.
Ray from object top through center of curvature.

The second ray points toward the center of curvature behind the mirror. Note that the light ray is square with the mirror at the intersection point. This means that the outgoing ray path traces over the incoming path and on past the object.

Place a straight edge so that it crosses the top of the object and the center of curvature. Draw the light ray from behind the object ending at the mirror surface. This light ray is shown in red.
Virtual, erect, and enlarged image.

We see that the real outgoing light rays diverge, so the image is virtual. Extend the light rays on the back side of the mirror as shown and sketch in the image.

This image is upright and reduced in size. It is a virtual image since it is formed by virtual rays.


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