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A convex mirror and convex lens of radiu...

A convex mirror and convex lens of radius of curvature 20 cm are placed on same axis with 30 cm separation. A point-like object is placed at 20 cm from convex lens and its image by this combination is obtained at object. What will be focal length of convex lens ?

Text Solution

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`rArr` Here, radius of curvature of convex lens `= O_2 C` = 20 cm
Object distance OP = u = -25 cm
Image distance OC = v = 30 + 20 = 50 cm
`rArr` Lens formula
`1/f = 1/v - 1/u = 1/50 + 1/25`
`therefore 1/f = (1+2)/(50) = 3/(50)`
`therefore f = (50)/(3) = 16.67 cm `
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