The function of any microscope is to enhance resolution, or the clarity of the image. However, because microscopes create an enlarged image, thus making it possible for us to see details that we would not be able to see with the naked eye, the magnification that microscopes provide is often confused with the resolution. The difference between magnification and resolution is rather profound. An image of the interior of a cell, with good magnification but poor resolution, suggests that a cell is filled with cytoplasm, but a microscope with great resolution will reveal the chloroplasts, ribosomes and membranes comprising the cytoplasm.
The human eye has the ability to detect separate entities as two separate objects, if the objects, when held 10 inches from the face, are 0.1mm apart. If the objects are magnified 10 times, then we will be able to detect them 0.01mm apart. Unfortunately, due to aberrations and artifacts in microscope lenses, sometimes, even if objects can be made to appear 0.1mm apart, the edges are so blurry that we lose the ability to see two separate objects.
Eye pieces of markedly different magnifications can provide the same magnification when used in a microscope, if combined with objective lenses of the appropriate power. For instance, a 40x objective and 5x ocular lens, used together, will give 200x magnification, as well a 20x objective and 10x ocular lens. The two lens combinations will, however, give different resolutions, if the numerical apertures of the lenses differ.
When viewing objects under a microscope, image resolution depends directly on numerical aperture, or the angle of the cone of light entering the objective lens, as well as the wavelength of the light hitting the objects. A larger numerical aperture and a lower wavelength both result in a higher degree of resolution, according to the equation: resolution = (Numerical Aperture)/(.61* wavelength). Increase the numerical aperture by increasing the angle of incidence of light onto the objective lens or by purchasing special objective lenses with high degrees of refraction. Decreasing the wavelength is the most practical and effective way of increasing resolution.