Q: To fit a contact lens to a patient\'s eye,a keratometer can be used to measur
ID: 1749356 • Letter: Q
Question
Q: To fit a contact lens to a patient's eye,a keratometer can be used to measure thecurvature of the cornea-the front surface of the eye. Thisinstrument places an illuminated object of known size at a knowndistance p from the cornea, which then reflectssome light from the object, forming an image of it. Themagnification Mof the image is measured by using asmall viewing telescope that allows a comparison of the imageformed by the cornea with a second calibrated image projected intothe field of view by a prism arrangement. Determine the radius ofcurvature of the corneawhen p = 32.0 cmand M = 0.0170. Q
mm
Q
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Explanation / Answer
Given : Objectdistance P = 32 cm Magnification M = - Q / P = 0.0170 Image distance Q = - 32 * 0.0170 = - 0.544 cm We know that : 1 / f = 1/P + 1/ Q = 1 / 32 - 1 / 0.544 f = - 0.553 cm We have : Radius of curvature R = 2 f = 2 * -0.553 = - 1.106 cm = - 11.06 mm Hope this helps u!Related Questions
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