Final answer:
In a confocal laser scanning microscope, a finely focused laser beam is used to illuminate the specimen.
Step-by-step explanation:
In a confocal laser scanning microscope, a finely focused laser beam is used to illuminate the specimen. Laser light illumination tends to be quite intense, which is important for observing details at higher magnifications. It is necessary to ensure that the light does not result in the degradation of the specimen.