Magnifying Power Simple Microscope

Magnifying Power of a Simple Microscope

Magnifiers

Simple microscopes are usually termed magnifiers, and, when consisting of one or more lenses, always remain simple. The most common are those with one or several double-convex lenses.

The shorter the radii (the more curved the surfaces) are in these, the greater will be the magnifying power, and the higher this is, the less of the object's surface can be seen at once. Each additional lens increases the magnifying power in proportion to its curvature. The distance between the lens and the object, when this is seen most distinctly, is called the focus ; at the point where the object is most distinct, the lens is said to be in focus ; when indistinct or blurred, out of focus.

Unless a microscope is known to come from the hands of a reliable firm, any claim as to magnifying power should be accepted with reserve. In former years, when the country was overrun with cheap foreign productions, the most fanciful claims were made in this direction.

It is evident that a lens magnifies an object equally in all directions ; this is said to be in areas, and is the square of the linear, so that if an object is magnified 4 times in the linear, it is 16 times in area. The commonly accepted term to express magnifying power of simple, as well as compound microscopes, is in diameters (linear}. A single lens of 1 inch focus magnifies about ten diameters ; one of 2 inch focus, about 5 diameters ; one of a 1/2 inch focus, 20 diameters, and so on. In a lens of high magnifying power, the focus is ordinarily about twice the diameter, so that if a lens is 1/2 inch diameter its focus is about 1 inch.

This may, however, be more accurately determined by projecting, say a flame or window frame, upon a white piece of paper ; the distance between the paper to the center of the lens, when the image is most distinct, is its focal distance. When a lens is two inches or more in diameter, it is usually termed a reading glass.

Using Magnifiers

In using magnifiers the lens should be held close to the eye and such a position taken that the object will receive the best illumination. In the lenses of equally convex surfaces, it is immaterial which side is held toward the eye ; but when plano-convex lenses are used, the plane side should always be toward the eye, as it gives the flattest field.

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