The part of a microscope you look through to see specimens is the eyepiece, also called the ocular lens. It sits at the top of the microscope’s viewing tube and magnifies the image formed by the objective lens.
Most school and laboratory microscopes use eyepieces with 10× magnification, although other powers are available. If a microscope has a 10× eyepiece and a 40× objective lens, the total magnification is 400×, calculated by multiplying the two lens powers.
The eyepiece is different from the objective lens. The objective is the lens positioned closest to the specimen and usually provides most of the magnification. A binocular microscope has two eyepieces for viewing with both eyes, while a monocular microscope has one. Looking through the eyepiece alone does not guarantee a clear image; focus, illumination and specimen preparation also matter.