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Question
AB is the object, A'B' is the image, and MM' is the position of the mirror. Complete the ray diagram showing the formation of the image and find the focal length of the mirror.

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Solution
A light ray coming from a point on object AB is reflected from the surface of the mirror, it passes through the principal focus and the other ray passing through the center of curvature strikes the mirror normally i.e. 90 degrees. Hence it will reflect back. These two reflected rays coincide at a point where the image is formed. The image, A'B' is real, inverted, and diminished in size. The focal length was found to be 16 mm.

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