Final answer:
The objective lens is responsible for collecting focused light rays on the specimen in a microscope after they pass through the condenser lens.
Step-by-step explanation:
The component responsible for collecting light rays that have been focused on the specimen is the objective lens. Its role is crucial in the microscopy process. After light from an illuminator passes through the condenser lens and is focused on the specimen, the objective lens then collects this light to form an image. As the magnification of the objective lens increases, the length of the lens increases, and the aperture decreases, necessitating adjustments to the illumination to maintain a clear image. This can include moving the condenser lens closer or further from the specimen, adjusting the iris diaphragm, or altering the light intensity.