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Problem 36.3: Check vision, prescribe glasses

Please wait for the animation to completely load.

This animation models the eye (position is given in arbitrary units and angle is given in degrees). The slider can be used to simulate the eye's ability to accommodate. When the eye is in a relaxed state, the focal length of the lens system of the eye is taken to be one. Notice that as the eye accommodates, focusing on nearby objects, the focal length of the eye decreases. The location of the near source can be changed by dragging the source. The focal length of the eyeglass can be altered by clicking on the eyeglass and then dragging the hotspots. Restart.

  1. Is the eye represented in the animation normal, nearsighted, or farsighted?
  2. If the eye is nearsighted, what power eyeglasses should be used for normal vision? (The eye can see faraway objects when relaxed, and also focus on an object at x = 2.0.)
  3. If the eye is farsighted, what power eyeglasses should be used to allow the person to see an object at x = 2.0? Would a farsighted person with these glasses still be able to focus on a faraway object? Why are farsighted individuals often prescribed bifocals?

Problem authored by Melissa Dancy and Wolfgang Christian.

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