Multi-immersion, for oil, water, and glycerin. Phase lenses are generally not as good for fluorescence applications as the light transmission is reduced by the presence phase ring inside the lens. As stated before, this is obvious and self-explanatory. Numerical Aperture . After the imprint of the magnification on any quality objective lens, there is usually a slash followed by a number which may be anything from 0.035 to 1.4.
Resolution is defined as the ability of a lens to distinguish between small objects.
Obviously, this differs greatly from magnification which is just the ability of the lens to enlarge the image of an object. It does not mean that you will necessarily be able to resolve details in the object. Tube Length and Coverslip Thickness . The number after the slash is the thickness in millimeters of the cover glass for which the objective was designed and corrected. For most objectives for close working distance, this number is 0.17 .