Final answer:
The rotating nosepiece, or turret, is the microscope part beneath the ocular lenses that secures the objective lenses and enables their rotation.
Step-by-step explanation:
The part located below the ocular lenses and serves as an attachment point for the objective lenses is called a rotating nosepiece or turret. This structure allows the user to switch between different objective lenses, typically ranging in magnification from 5x to 100x, without losing focus on the sample. This is because objective lenses are set up to be parfocal, a feature that keeps the specimen in focus when changing magnification levels.
Each objective lens works in conjunction with the ocular lenses to produce a magnified image, with total magnification being the product of the ocular and objective magnifications. The overall function of a microscope is to magnify small objects, and the nosepiece mechanism is a crucial part of achieving this.