An OCULAR, also known as an EYEPIECE, is a part of a microscope that is used to magnify the image. It is usually composed of several lenses and is placed at the end of the microscope tube. An OPTIC is a LENS or system of lenses used to refract light in order to form an image. A LENS is a curved piece of glass or other transparent material used to refract light in order to form an image. All of these parts are essential components of a microscope and are necessary for it to function properly.