Editing Objective (optics) (section)

===Immersion lenses===
Some microscopes use an [[oil-immersion objective|oil-immersion]] or [[Water immersion objective|water-immersion]] lens, which can have magnification greater than 100, and numerical aperture greater than 1. These objectives are specially designed for use with [[Index-matching material|refractive index matching oil]] or water, which must fill the gap between the front element and the object. These lenses give greater resolution at high magnification. Numerical apertures as high as 1.6 can be achieved with oil immersion.<ref>{{cite web |url=http://www.olympusmicro.com/primer/anatomy/objectives.html |title=Microscope objectives |work=Olympus Microscopy Resource Center |first=Spring |last=Kenneth |author2=Keller, H. Ernst |author3=Davidson, Michael W.  |access-date=29 Oct 2008}}</ref>