Worlds of David Darling
Encyclopedia of Science
Home > Encyclopedia of Science


reflection goniometer
Reflection goniometer
An instrument for measuring angles, especially those between crystal faces. The simplest form is the contact goniometer, a protractor whose base is laid against one face, a movable arm being turned until it contacts the adjacent face. The more accurate reflecting goniometer mounts the crystal axially on a graduated circle, or more usually two graduated circles, horizontal and vertical, rotatable independently. The crystal is rotated until each face in turn reflects a collimated light beam into a fixed telescope, and so the direction of the normal to each face is determined. (The term may also be used for the direction finder.)

Related category