# An object is 8cm high. It is desired to form a real image 4cm high at 20cm from the lens. The focal length and power of lends are

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An object is 8cm high. It is desired to form a real image 4cm high at 20cm from the lens. The focal length and power of lends are
A. convex mirror with focal length f=40cm
B. convex mirror with focal length f=20cm
C. convex mirror with focal length f=-40cm
D. convex mirror with focal length f=-240cm

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