A man can see upto 5 metre clearly. To see clear upto 10 m, the focal length of lens will be
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For correcting vision, use the lens formula \(\frac{1}{f} = \frac{1}{v} - \frac{1}{u}\), where \(v\) is the object distance and \(u\) is the image distance.
The lens formula determines the focal length needed for vision correction. If someone sees clearly only at 5 meters, a -5 meter focal length lens is needed to correct their vision to 10 meters.