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  • Vision is arguably the most compelling human sense. Words and stories and sounds allow

  • us to imagine strange beasts and faroff worlds, but seeing makes us truly believe they exist.

  • And that's why we place so much effort into correcting the optics of our eyes when they

  • don't work - whether with glasses or contact lenses or surgery. But if you're in a pinch,

  • bleary-eyed or missing your glasses, there's a simple trick that will allow you to see

  • clearly - just make a tiny, tiny hole using your fingers, look through it, and the world

  • will become clear again. This works no matter how blurry your vision is -- take off your

  • glasses and give it a try!

  • Amazing, right?! But to explain this wizardry, we just need to remember how seeing works.

  • Light travels outwards from a source, bounces off of objects in its path, travels into your

  • eye and onto your retina, where it forms an image. If your eye had no lens, light from

  • a single source would hit your retina in lots of places and result in a smeared-out mess

  • - which is exactly what happens when I take the lens off of my camera.

  • A lens focuses that spread-out light back into a single point, corralling it into a

  • crisp image on your retina. And after a little excitation of light-sensitive nerves and interpretation

  • from your brain, you see.

  • But wait! When we look at an object, the background and foreground are usually blurry, because

  • a lens can only focus light coming from one distance away. If an object is too near or

  • too far, its light will again be spread out on your retina leaving you with a blur. Fortunately,

  • muscles in our eyes allow us to accommodate by squeezing the lens, which changes its focal

  • length so we can see at different distances - except when we can't, or when our lenses

  • become damaged - in which case we need glasses.

  • Unlike a lens, a pinhole or other small opening can focus light coming from ANY distance:

  • because it's such a small opening, it only allows light to come through in one place,

  • and thus in only one direction from any particular source. So there's no blur, and everything

  • is in focus!

  • If you're familiar with photography, this is why using smaller and smaller apertures

  • makes everything in your photo come into focus.

  • Of course, small openings like pinholes and camera apertures create crisp images by blocking

  • rather than focusing light, so the images are much darker -- which is a major reason

  • why we use lenses rather than pinholes for glasses, telescopes -- and eyes.

  • And yet, in a pinch, looking through a tiny hole made with your fingers can help

  • you see. Now do you see why?

Vision is arguably the most compelling human sense. Words and stories and sounds allow


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B1 中級

メガネなしで見る方法 (How to See Without Glasses)

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    HechTea に公開 2021 年 01 月 14 日