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A convex lens forms a real and inverted ...

A convex lens forms a real and inverted image of a pencial at a distance of 60 cm from the lens. The image formed is of the same size as the object. Find the focal length and power of the lens. At what distance is the pencil placed from the lens. ?

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Data : Convex lens, v = 40 cm M = -1, f = ? `h_(1)= ? , u = ? `
` M = -1 = v/u`
v = -v = -40 cm
The pencil is placed at 60 cm from the convex lens.
` 1/f = 1/u = ( 60 cm) = 1/( - 60 cm) = 2/( 60 cm)`
` f = (40 cm)/2 = 30 cm `
The focal length of the lens = 30 cm
` P = 1/f= 1/(30 cm) = 1/(0.3 m) = 3.3D`
The power of the lens = 3.3 D
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