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Question Video: Determining the Type of Lenses Used to Correct Nearsightedness Science

Which of the following types of lenses can correct nearsightedness? [A] Concave [B] Convex

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Video Transcript

Which of the following types of lenses can correct nearsightedness? (A) Concave, (B) convex.

Let’s first remember what it means for an eye to be nearsighted. When an eye is healthy, it takes on roughly the shape of a sphere. It’s possible though for an eye to be misshapen or deformed. This changes the way the eye focuses incoming rays of light. When a nearsighted eye, like this, looks at an object that’s very near the eye, the eye is able to bend those incoming rays of light so that they meet at the back of the eye, called the retina. When this happens, the up close object, whatever it is, is clearly seen.

The problem with a nearsighted eye shows up when it looks at objects far away. A nearsighted eye bends these incoming rays so that they cross before they get to the back of the eye. Because the rays are not focused at the back of the eye, the faraway object looks blurry.

The vision of a nearsighted eye can be corrected using a lens. The two main types of lens are convex and concave. A convex lens brings parallel incoming rays to a focus, while a concave lens spreads out incoming parallel rays. So let’s think. With our nearsighted eye, light from objects far away is focused so that the rays meet before they reach the back of the eye. We could say, in other words, that this eye focuses light from faraway objects too much.

To move this focus point to the back of the eye, we could put a concave lens in front of it. This way, light coming in from a faraway object is spread out so that when the nearsighted eye focuses these rays, they do meet at the back of the eye, at the retina. Putting this concave lens in place in front of the nearsighted eye means the eye can even see faraway objects clearly. For our answer, we choose option (A). A concave lens can correct nearsighted vision.

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