Final answer:
When using a microscope, specimens need to be illuminated to form an image. Condensers are used to increase the intensity of light falling on the specimen. The type of condenser used depends on how the specimen is examined.
Step-by-step explanation:
When using a microscope, we rely on gathering light to form an image. Most specimens need to be illuminated, particularly at higher magnifications, when observing details that reflect only small amounts of light. Special illuminating systems called condensers are used to increase the intensity of light falling on the specimen. The type of condenser depends on how the specimen is examined, whether by transmission, scattering, or reflecting.