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ultramicroscope ul·tra·mi·cro·scope (ŭl'trə-mī'krə-skōp')
A microscope with high-intensity illumination used to study very minute objects.
microscope arrangement used to study colloidal-size particles that are too small to be visible in an ordinary light microscope. The particles, usually suspended in a liquid, are illuminated with a strong light beam perpendicular to the optical axis of the microscope. These particles scatter light, and their movements are seen only as flashes against a dark background; their structure is not resolved.