Your Friend Needs Glasses

Your friend needs glasses with diverging lenses of focal length – 65.0 cm for both eyes. You tell him he looks good when he doesn’t squint, but he is worried about how thick the lenses will be. Assuming the radius of curvature of the first surface is R1 = 50.0 cm and the high-index plastic has a refractive index of 1.66,
(a) Find the required radius of curvature of the second surface.
(b) Assume the lens is ground from a disk 4.00 cm in diameter and 0.100 cm thick at the center. Find the thickness of the plastic at the edge of the lens, measured parallel to the axis. Suggestion: Draw a large cross-sectional diagram.

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