This is really noob question, I was thinking about how eye works and I dont understand this most basic thing.

Imagine a human looking at tiny omnidirectional source of light, like a small LED diode. The light from this infinitely small light source hits our whole eye, it reaches all of its surface yet we dont see our entire vision go white or red or whatever the color of the source is, we just see it as small spark, miniature "pixel", we can see that its small despite the light hitting our whole eye.

Why is that? When I imagine it, no matter how big or small, close or far, a omnidirectional source of light that is directly in front of eye will shine photons to entire cornea/pupil, why doesnt it then also cover our entire vision?


1 Answer 1


Light from the LED does hit all of the front of your eye. However, the front of your eye contains a lens that takes all light from a point and focuses it onto a point in the back of your eye. The back of your eye is called the retina, and that is where an image is formed. See the picture below.

The blue area at the front of the eye where light enters is called the cornea and the whitish oval is a lens. Both serve to change the direction of the light rays so that all rays from a single point converge to another point on the retina at the back of the eye. An image forms when different points of light get focused to different points on the retina (notice that the light from the top and bottom of the tree get focused to different points on the retina).

In fact, if you removed the lens from the eye, the light from the diode would hit all of the surface of the back of the eye, forming an image that was completely blurry.

Eye lens image formation

Taken from: https://opentextbc.ca/physicstestbook2/chapter/physics-of-the-eye/

  • $\begingroup$ "In fact, if you removed the lens from the eye, " Read about inter-ocular lenses ( IOL ) as a treatment for cataracts. The cloudy lens is disintegrated, suctioned out, and a replacement lens inserted... $\endgroup$
    – DJohnM
    Jun 30, 2019 at 0:15

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