In order to teach the principle of reflection by mirrors at Pacific University College of Optometry in the geometric optics laboratory course, a method and written laboratory procedure was developed. The optical spherometer, also known as a radiuscope, was chosen as a suitable presentation device since it requires the use of convex, concave, and plane mirror reflection to measure the radius of curvature of the mirror-like surface of a hard contact lens. Drysdale's apparatus was modified so that the optical bench design consisted of a non-collimated light source directed perpendicular to the bench and reflected off a glass plate set at 45°. A +20.00 diopter, double aspheric objective and a + 10.00 diopter, biconvex eyepiece were used to focus on the reticle image reflected from the contact lens surface and obtaining the radius of curvature. The goal of the lab experiment is to differentiate two contact lenses with different radii. It was determined from the range of measurement accuracy that two lenses, a 6 mm and 9 mm concave radius of curvature, be used to achieve repeatable experimental results.
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