Final answer:
The distance between the specimen and the objective lens in a microscope is called the working distance.
Step-by-step explanation:
The distance between the specimen and the objective lens in a microscope is called the working distance. It is usually measured in millimeters and is the distance from the front lens element of the objective to the specimen or cover glass.
The numerical aperture (NA) of a lens is related to its light-gathering ability and resolution but does not indicate the working distance. As one increases the NA and the magnification, the working distance typically decreases, which can increase the risk of damaging the specimen or the objective lens if they come into contact.
The distance between the specimen (letter) and the objective lens is called the working distance. This is the distance from the front lens element of the objective to the specimen or cover glass. The working distance decreases as the numerical aperture (NA) and magnification increase.