Final answer:
The subject of this question is Biology, specifically related to microscopes.
Step-by-step explanation:
The subject of this question is Biology. Specifically, this question is related to the topic of microscopes. In a compound microscope, the eyepiece is located at the base and can rotate. The eyepiece contains a lens called an ocular lens which typically magnifies images 10 times (10x). The eyepiece, also known as the ocular lens, of a microscope typically magnifies images 10 times (10x). At the opposite end of the microscope's body tube, you will find the objective lenses on a rotating nosepiece, which can usually magnify between 4x and 100x. The total magnification of an image seen through the microscope is calculated by multiplying the ocular magnification by the objective magnification. For instance, if you're using a 40x objective lens and a 10x eyepiece, the total magnification would be 400x. As the base of the eyepiece rotates, it allows for different objective lenses to be moved into place without losing focus on the specimen, a feature known as being parfocal.