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Farsightedness, also known as hyperopia, is a common vision condition where distant objects can be seen more clearly than nearby ones.
This occurs when the light entering the eye focuses behind the retina instead of directly on it. The primary cause of farsightedness is either the eyeball being too short or the cornea having too little curvature. Individuals with farsightedness often struggle with tasks like reading, as they have difficulty seeing objects up close.
Symptoms may include eye strain, headaches, or squinting when focusing on close work. To address this issue, corrective lenses are used. These lenses help to bend the light rays together more sharply, allowing them to focus on the retina instead of behind it. In our example, the man used eyeglasses with corrective power to assist with his vision while reading at a close distance.

Refractive power is a measure of how much a lens can bend light to focus on a specific point. It is expressed in units called diopters (D).
A lens with a higher diopter value has a greater refractive power and can bend light more effectively. The formula for calculating refractive power is given as: \[ P = \frac{1}{f} \]where \( P \) is the power in diopters and \( f \) is the focal length in meters. A positive refractive power indicates converging lenses, usually used for correcting farsightedness.
In the exercise, the man uses glasses with a refractive power of 3.80 diopters to correct his farsightedness, by bringing the focal point of light onto his retina.

When prescribing contact lenses, the refractive power needs to be accurately calculated because they sit directly on the eye.
Unlike eyeglasses, which are positioned some distance away from the eyes, contact lenses eliminate this gap, and thus, adjustments are necessary.In the problem, the glasses have a refractive power of 3.80 diopters.{The man wearing these glasses can read at a minimum distance of 0.280 meters. To maintain the same vision ability with contact lenses, we directly use this reading distance in our calculations.} The formula for calculating the refractive power needed for the contact lenses is:\[ P = \frac{1}{0.280} \approx 3.57 \, \text{diopters} \]This power compensates for the loss of distance between the lens and the eye present with glasses. Thus, the correct prescription for the contact lenses in this scenario is 3.57 diopters.