Contact lenses are placed right on the eyeball, so the distance from the eye to an object (or image) is the same as the distance from the lens to that object (or image). A certain person can see distant objects well, but his near point is 45.0 cm from his eyes instead of the usual 25.0 cm. Is this person nearsighted or farsighted?

검증된 단계별 안내

Step 1: Begin by understanding the terms 'nearsighted' and 'farsighted.' Nearsightedness (myopia) means a person can see nearby objects clearly but struggles to see distant objects. Farsightedness (hyperopia) means a person can see distant objects clearly but struggles to see nearby objects.

Step 2: Analyze the problem. The person can see distant objects well, but their near point is farther than the usual 25.0 cm. This indicates difficulty in seeing nearby objects, which is a characteristic of farsightedness.

Step 3: Relate the near point to the condition. A normal near point is 25.0 cm, but this person’s near point is 45.0 cm. This extended near point confirms that the person is farsighted.

Step 4: Conclude that the person is farsighted based on the given information and the definition of farsightedness.

Step 5: If needed, discuss corrective measures. Farsightedness is typically corrected using converging lenses (convex lenses) to reduce the near point distance and allow the person to focus on nearby objects.

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주요 개념

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Nearsightedness and Farsightedness

Nearsightedness (myopia) occurs when the eye is too long or the cornea is too curved, causing distant objects to appear blurry while near objects are seen clearly. Farsightedness (hyperopia) is the opposite, where the eye is too short or the cornea is too flat, making it difficult to see close objects clearly while distant objects may be seen well. Understanding these conditions is crucial for determining the type of vision correction needed.

Near Point

The near point is the closest distance at which the eye can focus on an object clearly. For a typical young adult, this distance is about 25 cm. If a person's near point is farther away, such as 45 cm, it indicates a problem with focusing on nearby objects, which is a characteristic of farsightedness.

Optical Correction

Optical correction involves using lenses to adjust the focal point of light entering the eye, allowing for clearer vision. For nearsighted individuals, concave lenses are used to diverge light rays, while convex lenses are used for farsighted individuals to converge light rays. Identifying the type of vision impairment helps in selecting the appropriate corrective lenses.