Final answer:
The question deals with optical measurements involving lenses, with 'root is 16mm' referring to a standard distance between focal points in a lens system. The 25 cm near point distance is the typical closest viewing range for the human eye.
Step-by-step explanation:
The phrase 'root is 16mm' seems to refer to an optical measurement, likely related to the distances involved in the optics of lenses or a microscope setup. Given the context provided, it appears that the 16 mm measurement is the standardized distance between the image-side focal point of the objective lens and the object-side focal point of the eyepiece. The distance mentioned, 25 cm, is a common near point distance, which is the closest distance at which the average human eye can see an object clearly. The focal distances for the objective lens (fobj) and the eyepiece (feye) are important for determining the magnification and the quality of the image produced by the optical instrument.