Magnification and Numerical Aperture: "40x/0.65" signifies a 40x magnification and a numerical aperture (NA) of 0.65, which relates to the objective's light-gathering ability and resolution. Phase Contrast: The "PH" or "Ph2" indicates it's designed for phase contrast microscopy, a technique used to enhance contrast in unstained, transparent specimens. Optical System: This objective is part of an infinity-corrected optical system, as suggested by the infinity symbol (?) and often seen in modern Zeiss objectives e. ICS - Infinity Color Corrected System.
Applications: Objectives of this type are suitable for routine microscopy in brightfield and phase contrast, and can often be used for epifluorescence work within the visible spectrum.