In bright field microscopy a specimen is placed on the stage of the microscope and incandescent light from the microscope’s light source is aimed at a lens beneath the specimen. This lens is called a condenser.
The condenser usually contains an aperture diaphragm to control and focus light on the specimen; light passes through the specimen and then is collected by an objective lens situated in a turret above the stage.
The objective magnifies the light and transmits it to an oracular lens or eyepiece and into the user’s eyes. Some of the light is absorbed by stains, pigmentation, or dense areas of the sample and this contrast allows you to see the specimen.
For good results with this microscopic technique, the microscope should have a light source that can provide intense illumination necessary at high magnifications and lower light levels for lower magnifications.