Light converging inside the eye

  • #26
Okay, I see what you mean. In this case the brain is being fooled because the rays are refracted to different angles when they come out of the water, so a straight line traced to the image would not intercept the object. Note that you have a cone of rays of differing angles entering your eye from every point source, so in reality your brain isn't tracing light rays back to their source, but extrapolating the position of objects based on the image formed on your retina. Hence the reason it can be fooled by refracted rays.

Certainly. That makes sense.
I have good eyes, so I don't wear spectacles, but I presume that the refraction of rays caused by glasses would change the angles of rays slightly and the brain would err slightly in extrapolating the exact location of the source, just like you've mentioned above?

Drakkith, I'm sincerely very grateful to you for persisting with such a dunce, ignorant fellow. Thank you so much!
 
  • #27
Drakkith
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I have good eyes, so I don't wear spectacles, but I presume that the refraction of rays caused by glasses would change the angles of rays slightly and the brain would err slightly in extrapolating the exact location of the source, just like you've mentioned above?

Not really. Glasses are designed to correct your vision, not to alter it. The combined effect of the lenses and your eye add up to normal vision.

Also, consider the following. When you place an object underwater, the light coming from it passes through the boundary and changes its angle before making its way to your eye. Now imagine looking through a fish tank at an object on the other side. The light passes through the far side, refracts, passes through the tank and refracts again. The two refractions (well, four really since there is an air-glass boundary and a glass-water boundary on both sides) cancel each other out in angle. (The same thing happens when looking through a normal window)
 
  • #28
Also, consider the following. When you place an object underwater, the light coming from it passes through the boundary and changes its angle before making its way to your eye. Now imagine looking through a fish tank at an object on the other side. The light passes through the far side, refracts, passes through the tank and refracts again. The two refractions (well, four really since there is an air-glass boundary and a glass-water boundary on both sides) cancel each other out in angle. (The same thing happens when looking through a normal window)
I understand. But surely that doesn't hold with spectacles since the front and back surfaces aren't parallel and it would defeat the whole purpose of using spectacles anyway.

Thank you once again. No more questions. =D
 

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