Final answer:
A darkfield microscope uses a cone of light which indirectly illuminates the specimen to produce a bright image against a dark background by allowing only refracted or reflected light to reach the objective lens.
Step-by-step explanation:
The type of microscope that uses a cone of light so that light only hits the specimen indirectly, producing a light image on a dark background, is known as a darkfield microscope. In darkfield microscopy, a small, opaque disk is placed between the illuminator and the condenser lens to create a hollow cone of light that is focused on the specimen. Only light refracted or reflected by structures in the specimen reaches the objective, which results in bright objects appearing on a dark background.