T720 Series Microscope
AmScope Proprietary Page 45 of 46
Nosepiece
This circular structure is where the different objective lenses are
screwed in. To change the magnification power, rotate the turret.
Numerical Aperture (N.A.)
N.A. is a rating for the resolution of the objective lens. The N.A. rating ranks the
objective lens’ ability to capture light and show fine detail.
Lens with larger numerical apertures capture finer details than lenses with smaller
numerical apertures. Generally, lenses with larger numerical apertures create a brighter
image, but the depth of field will be shallower.
N.A. Rating
Objective
Lens
Average
Numerical
Aperture
4X 0.1
10X 0.25
40X 0.65
100X 1.25
Parcentered
When changing objectives, the image of the specimen stays centered. Most compound
microscopes are parcentered.
Parfocal
When changing objectives, the image of the specimen stays in focus without
needing to adjust the coarse focusing knob. Not all compound microscopes are
parfocal.
Tension Knob
The large, innermost ring on the focusing knob.
Adjusts the tension of the focusing knobs.
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