A person uses `+ 1.5 D` glasses to have normal vision from `25 cm` onwards. He uses a `20 D` lens as a simple microscope to see an object. Calculate the maximum magnifying power, if he uses the microscope (a) together with his glasses (b) without the glasses.
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Here, `P_(1) = 1.5 D : d = 25 cm`, `P_(2) = 20 D` (a) with glasses on `M = 1 + (D)/(f_(2)) = 1 + (25)/(100//20) = 6` (b) without glasses, Focal length of glasses, `f_(1) = (100)/(P_(1)) = (100)/(1.5) = (200)/(3)cm`. `u = - 25 cm, v = ?` As `(1)/(v) - (1)/(u) = (1)/(f_(1))` `:. (1)/(v) = (1)/(f_(1)) + (1)/(u) = (3)/(200) - (1)/(25) = (3 - 8)/(200) = (-5)/(200)` `v = - 40 cm`. `M = 1 + (v)/(f_(2)) = 1 + (40)/(100//20) = 9`
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