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The role of refraction in vision

  1. Feb 3, 2013 #1
    I read the following in a book.
    “In order for there to be a clear image on your retina, the eye must refract the light rays. About two thirds of the refraction occurs at the surface of the eye. If water is on the eye, nearly all of the refraction is lost because the refractive index of the material is approximately that of the water.
    Wearing goggles provides a layer of air to give you normal refraction.”
    This is probably a question with an obvious answer. So the refraction is necessary to focus the light on the retina and if there is no refraction the light just travels through the lens of the eye and arrives spread out on the surface of the retina?
  2. jcsd
  3. Feb 3, 2013 #2
    Naturally, Yes. But difraction may be in use too. There is a sort of googles, black with a lot of tiny holes for yey training. I don't think it makes any training, but allows to see without proper focusing
  4. Feb 3, 2013 #3


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    The lens also refracts the light :-)
  5. Feb 3, 2013 #4


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    For practically all realistic purposes, the answer to your question is yes. Refraction is necessary, otherwise the light will be entirely out of focus when it arrives at the retina.
  6. Feb 5, 2013 #5
    Note that eye is also camera obscura. You could get a sharper image, even without any refraction, if the pupil could contract - with no refraction but with iris blocking light, the point spread function would be pupil size. Until the pupil gets so small that the Airy disc at retina starts to grow relative to the pupil.

    The pupil of man relies on refraction and cannot contract to size where resolution would be dominated by diffraction.
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