The ocular lens is close to the viewer's eye and provides a second level of magnification. Total magnification is the magnification of the objective multiplied by the magnification of the ocular. Practical maximum resolving power of a light microscope is limited by the wavelength of visible light. The smallest r achievable by light microscopy is 0.2 microns. The wavelength of electron beams is much smaller than that of light.
Specimen appears relatively dark against a bright background.
Relies on specimens having some contrast. Rather than receiving light directly from the condenser lens, the objective receives light reflected by the specimen. The result is that the specimen appears bright against a dark background. Out of phase light rays result in a higher-contrast outline of the specimen. Many types of unstained, living microorganisms show little contrast from their surrounding medium when using an ordinary light microscope.