Types of Microscopes,LightBright fieldDark-fieldElectronScanningTransmission,Brightfield Illumination,Dark objects are visible against a bright background.Light reflected off the specimen does not enter the objective lens.,The Compound Light Microscope,In a compound microscope, the image from the objective lens is magnified again by the ocular lens.Total magnification =objective lens ocular lens,Refractive index: The light-bending ability of a medium.The light may bend in air so much that it misses the small high-magnification lens.Immersion oil is used to reduce refraction of light (keep light from bending).,Figure 3.3,The Compound Light Microscope,