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प्रश्न
Magnifying power of a simple microscope is inversely proportional to the focal length of the lens. What then stops us from using a convex lens of smaller and smaller focal length and achieving greater and greater magnifying power?
उत्तर
Firstly, the process of making lenses with very short focal lengths (thick lenses) is not easy; secondly, as the focal length decreases, the defect of aberration in the lenses starts increasing. Due to this, the images formed by them become unclear. In reality, a single convex lens cannot achieve a magnification of more than 3, but a lens without an aberration defect can achieve a much higher magnification (about 10).
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| A compound microscope consists of two converging lenses. One of them, of smaller aperture and smaller focal length, is called objective and the other of slightly larger aperture and slightly larger focal length is called eye-piece. Both lenses are fitted in a tube with an arrangement to vary the distance between them. A tiny object is placed in front of the objective at a distance slightly greater than its focal length. The objective produces the image of the object which acts as an object for the eye-piece. The eye-piece, in turn, produces the final magnified image. |
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