Obtaining an image of a microscopic object

When we see an object, light rays bounce off (are diffracted by) the object and enter the eye through the lens, which reconstructs an image of the object and focuses it on the retina. In a simple microscope, an illuminated object is placed just beyond one focal point of a lens, which is called the objective lens. The lens collects light diffracted from the object and reconstructs an image beyond the focal point on the opposite side of the lens, as shown in Fig. 2.1. 

For a simple lens, the relationship of object position to image position in Fig. 2.1 is (OF)(IF1) = (FL )(F L ). Because the distances FL and F L are constants (but not necessarily equal) for a fixed lens, the distance OF is inversely proportional to the distance IFPlacing the object near the focal point 

F results in a magnified image produced at a considerable distance from F on the other side of the the lens, which is convenient for viewing. In a compound microscope, the most common type, an additional lens, the eyepiece, is added to magnify the image produced by the objective lens. 

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