s used to get in the right general visual range, whereas the fine adjustment knob is used to bring the image into maximally sharp focus. Finally, the nosepiece is used to change between objective lenses of different magnification powers; this is done by simply rotating the piece.
Mechanisms of Magnification
The total magnification power of a microscope is simply the product of the objective lens magnification and the eyepiece lens magnification. This might be 4x for the objective and 10x for the eyepiece for a total of 40, or it might be 10x for each type of lens for a total of 100x.
As noted, some objects have more than one objective lens available for use. A combination of 4x, 10x and 40x objective lens magnification levels is typical.
The function of the condenser is not to magnify light in any way, but to manipulate its direction and angles of reflection. The condenser controls how much light from the illuminator is permitted to pass up through the aperture, controlling the intensity of the light. It also, critically, regulates the contrast. In darkfield microscopy, it is the contrast between different, drab-colored objects in the visual field that is most important, not their appearance per se. They are used to tease out images that might not appear if the apparatus were simply used to bombard the slide with as much light as the eyes above it could tolerate, leaving the viewer to hope for the best results.
About the Author
Kevin Beck holds a bachelor's degree in physics with minors in math and chemistry from the University of Vermont. Formerly with ScienceBlogs.com and the editor of "Run Strong," he has written for Runner's World, Men's Fitness, Competitor, and a variety of other publications. More about Kevin and links to his professional work can be found at www.kemibe.com.