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Illustration 33.2: Flat Mirrors

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This animation shows images in two flat mirrors placed at an angle to each other. You can adjust the angle between the mirrors by click-dragging the green dot, and you can change the object size by click-dragging the red dot. The gray dots are the images. If you double-click in the animation window, you can see the path of some of the light rays from the source.

The yellow rays show the actual path of the light, while the gray "rays" show where it looks like the reflected yellow rays come from. When we look at objects, we assume light travels in straight lines (this is how our brain interprets the input it gets from our eyes). So when we look in a mirror, the images we see are behind the mirror because it looks like the light comes from the point behind the mirror. Since the light rays do not actually pass through the image points, the images are virtual ones. Try adjusting the angle between the mirrors to get more than two images. Why are there multiple images? Double-click to see the light rays and identify the images that are a result of light reflecting off the mirror more than once. Identify points where multiply reflected light rays cross. If you were located there, you would see multiple images. Follow each ray straight back to the virtual image to check. Note that since there are only a finite number of rays drawn, you may not get every ray you expect to see. As you decrease the angle between the mirrors, why are there more images?

Illustration authored by Anne J. Cox.
Applet authored by Fu-Kwun Hwang.

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