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Two lenses have power +20&-40. What is the nature & focal length of each lens?An object is kept at 100cm from the lens power -40. Calculate the image distance |
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Answer» The value of magnification for convex lense is 1 and for concave lens is 0.2 Explanation: Given DATA: Power of lenses: +2D and - 4D +2D indicates that the lens is converging lens (convex lens) Distance of object p =1/f i)-4D indicates that the lens is diverging lens (concave lens) Therefore the focal length is -25 cm *To calculate the image distance for convex lens u = -100 cm f 50 cm V= (fx u)/(f-u) = 100 cm V= -(fx ul/(f+u) V -20 cm magnification =v/u = 20/100 =0.2 |
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