To fi t a contact lens to a patients eye, a keratometer

Chapter 23, Problem 23.32

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To fi t a contact lens to a patients eye, a keratometer can be used to measure the curvature of the corneathe front surface of the eye. This instrument places an illuminated object of known size at a known distance p from the cornea, which then refl ects some light from the object, forming an image of it. The magnifi cation M of the image is measured by using a small viewing telescope that allows a comparison of the image formed by the cornea with a second calibrated image projected into the fi eld of view by a prism arrangement. Determine the radius of curvature of the cornea when p _ 30.0 cm and M _ 0.013 0.