Introductory Microbiology

Bright field microscopy

• In bright-field microscopy, the microscopic field (the area observed) is brightly lighted and the microorganisms appear dark because they absorb some of the light. Ordinarily microorganisms do not absorb much light, but staining them with a dye greatly increases their light absorbing ability resulting in greater contrast and color differentiation. The optical parts of a typical bright field microscope and path the light rays follow to produce enlargement, or magnification of the object (Fig 4-2).Generally, microscopes of this type produce a useful magnification of about x 1000 to x 2000.