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A keratometer is an optical device used to measure the radius of curvature of the eye’s cornea—its entrance surface. ?
This measurement is especially important when fitting contact lenses, which must match the cornea’s curvature.
Most light incident on the eye is transmitted into the eye, but some light reflects from the cornea, which, due to its curvature, acts like a convex mirror.
The keratometer places a small, illuminated ring of known diameter 7.5 cm in front of the eye. The optometrist, using an eyepiece, looks through the center of this ring and sees a small virtual image of the ring that appears to be behind the cornea. The optometrist uses a scale inside the eyepiece to measure the diameter of the image and calculate its magnification.
Suppose the optometrist finds that the magnification for one patient is 0.049.
What is the absolute value of the radius of curvature of her cornea?
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