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MICROSCOPES
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MICROSCOPES
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Different types of lenses in the microscope can cause rays to travel in different directions depending on the angle of the incident or source rays. Light rays going through the lens can cause the light to converge or diverge, depending on whether the lens is concave or convex. Biconvex (converging) lenses are thickest at the center and biconcave (diverging) are thinnest at the center. There are many varieties of lenses that can be utilized with an optic system.
The focal length or focal distance is the distance between the center of a converging thin lens and the point at which parallel rays of incident light converge; or the distance between the center of a diverging lens and the point from which parallel rays of light appear to diverge. The point at which it intersects the focal plane is called the "focal point." The distance from the lens to the image is called the "optical element-image distance." Light going through a double convex (biconvex) lens will converge at a focal point. If a biconvex lens is near an object inside its focal point, a virtual upright image can be seen. The lenses of the microscope’s eyepiece (closest to your eye) create a virtual image because your eye is within the focal point. The eyepiece will only enlarge the image of the specimen. The objective (lens closest to the specimen) focuses on the specimen outside the focal point creating a real image. This image from the objective actually increases the detail or resolving power of that specimen. Resolution of the microscope is what allows the human eye to see detail they cannot see with the naked eye. It allows the viewer to enter the microworld. The higher the objective lens the better the resolution. The eyepiece does not contribute anything new to the image; it simply spreads out the details. This is referred to as empty magnification. This is why eyepieces are always less than 20 times magnification.
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