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Define the magnifying power of a compound microscope when the final image is formed at infinity. Why must both the objective and the eyepiece of a compound microscope has short focal lengths ? Explain. |
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Answer» Solution :The angular magnification (or magnifying POWER) of a microscope is DEFINED as the ratio of the angle subtended by the final image at the eye to the angle subtended by the object at the eye when seen directly. Angular magnification of a compound microscope when final image in a microscope is FORMED at infinity, is given by the relation : `m=-L/f_(0).D/f_(e)` Here L = length of microscope, D = least distance of DISTINCT vision, `f_0` = focal length of OBJECTIVE lens and `f_(e)` = focal length of eye piece. As magnifying power m is inversely proportional to both `f_0` and `f_(e)`, hence we prefer both objective and eyepiece to be of short focal lengths so as to have a high value of magnifying power |
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