The primary light gathering optic of a refraction telescope, located opposite of the eyepiece
in a compound microscope or a telescope, the lens closest to the object being viewed
The second of two figures quoted on a pair of binoculars that indicates the diameter of the lens furthest away from your eye when you're looking through them It's quoted in millimeters and the first figure is the magnification A 10x50 pair, for example, has 10x magnification with a 50mm objective lens
The lens of the eyepiece The ratio of the focal length of the objective lens to that of the mirror determines the magnification
The lens closest to the object In a stereo (low power) microscope there are objective pairs, one lens for each eyepiece lens This gives the 3-D effect On a high power binocular model there is still only one objective lens so no stereo vision
In an optical device using compound lenses, the lens closest to the object observed