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You are given two convex lenses. a. What is the focal length of the combined lens formed by the lenses put in contact ? b . What is the advantage in the combination ? c. if one of the lenses is concave, how will you find its focal length with the help of lens combination ? |
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Answer» Solution :`a.(1)/(F) = (1)/(f_(1)) + (1)/(f_(2))` F - Focal LENGTH of COMBINATION of lenses `f_(1)` - Focal length of one lens `f_(2) -` Focal length of second lens `f_(2)` - Focal length of second lens b, i. increases magnifying power . ii. For ERECTING an IMAGE. c. the focal length .f. of CONVEX lens and .F. of the lens combination can be found out by u-v method. Let `f_(2)` be the focal length of the concave lens. Then `(1)/(f_(2)) = (1)/(F) - (1)/(f_(1))` Knowing `f_(1) and F, .f_(2).` can be found out . |
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