Chapter 35, Problem 12P

You are training to become an optician’s assistant. One day, you are learning how to fit a contact lens to a patient’s eye. You make a measurement with a keratometer, which is used to measure the curvature of the eye’s front surface, the cornea. This instrument places an illuminated object of known size at a known distance p from the cornea. The cornea reflects some light from the object, forming an image of the object. The magnification M of the image is measured by using a small viewing telescope that allows comparison of the image formed by the cornea with a second calibrated image projected into the field of view by a prism arrangement. As part of your training, the optician has required that you do not use the automatic calculator associated with the machine, but must perform the calculations yourself. You must determine the radius of curvature R of the cornea for the measurements you make for the patient: p = 30.0 cm and M = 0.013 0.