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| | Nikon MicroscopyU: Interactive Java Tutorials - Focusing and Alignment Mercury and Xenon Arc Lamps |
 | | In a mercury arc lamp, plasma balls are located adjacent to both the cathode and anode, and each has approximately the same intensity, which is twice that in the center of the arc. |
 | | The arc itself is very small (about 1 or 2 millimeters in length), and the image of the arc must be positioned along the optical axis of the microscope, at the center of the condenser aperture in the vertical illuminator, to ensure even illumination. |
 | | Regardless of whether alignment of the arc is accomplished with the aid of an accessory or with a white piece of paper placed on the microscope stage, both methods project the arc image that is present at the entrance pupil of the objective, in effect, the rear objective aperture. |
| www.microscopyu.com /tutorials/java/arclamp/index.html (2009 words) |
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