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If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective lens of focal length 5 cm, the focal length of the eye-piece should be close to: |
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Answer» 2 mm If FINAL image is OBTAINED at near point, then magnification, `m=(L)/(f_0)(1-(D)/(f_e))` `375=(150)/(50)(1+(25)/(f_e))` `(375)/(3)=1+(25)/(f_e)` `123-1=(25)/(f_e)` `f_e=(25)/(122)` `thereforef_e=0.2049`mm`therefore~~0.2` mm Case-II : If final image is obtained at infinity, then magnification, `m=(L)/(f_0)((D)/(f_e))` `375=(150)/(50)((25)/(f_e))` `(375)/(3)=(25)/(f_e)` `thereforef_e=(25xx3)/(375)``thereforef_e=0.2` mm |
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