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An optical instrument uses a lens of power 100 D for objective lens and 50 D for its eyepiece. When the tube length is kept at 25 cm the final image is formed at infinity. (a) Identify the optical instrument. (b) Calculate the magnification produced by the instrument. |
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Answer» Solution :Here focal LENGTH of objective lens `f_(0)= (1)/(P_(0))= (1)/(100) `m =0.01 m = 1.0 cm , focal length of eyepiece `f_(e) = (1)/(P_(e)) = (1)/(50) m = 0.02 m = 2.0 ` cm length of the tube L = 25 cm and final image is being formed at infinity. (a) The instrument is a compound microscope because both `f_(0)` and `f_(e)` ,are small and comparatively speaking `f_(0) LT f_(e)` (b) Magnification produced m =- `(L.D)/(f_(0).f_(e))=- ((25cm)xx(25 cm))/((1.0 cm)xx(2.0cm))=-312.5` |
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