The question title might be a misnomer, help me improve it.

My question is, from my understanding, a light travels in all direction from it's origin point. Also I assume that in the example of a flash light, the light won't travel back into the barrel of it since it is a physical object and it would stop the light (if it's under uv wavelength) besides there's a reflective mirror in there to make it go back forward.

In the case of a monitor, tv sets (crt or led or otherwise), or cellphone led.

I don't understand, how aligning small dots on the screen can provide an image that is crisp and clear instead of a blob of light which is blurred. (diffused) When thinking about the physicality of light, it doesn't seem possible for monitors to exist, I imagine that it would simply look the same as when one uses a camera to film something under low light and then suddenly points it at the bright monitor. Before the camera has time to make it's adjustments the monitor will appear like a big blob of light.

Why can we see an image on the screen? (I think I understand that it's a series of dots lit one after the other at a speed faster than the human eye can perceive giving the illusion of a continuous state of image as a whole.) But why doesn't the light, in some sense, "corrupt" it's neighbor?

At first I thought, maybe the light is directional like a laser, but then, if that were the case, that would mean I could only view the image from a certain angle, but unless I have a privacy screen on, I can view my phone, my computer, etc.. at more than one angle. Some monitors wider viewing angle than others, so I suppose it's directional in one sense. And yet two people can look at the monitor and see the same image albeit from the changed perspective of their relative location but the image is still nonetheless the same.

What is the physics behind this. Why is the white pixels displaying the white background behind this text not creeping on top of this black font, like a zerg creep would on Mar Sara?

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    $\begingroup$ That's what the lens in your eye is for: it focuses light rays that come from a certain angle on a small point in your retina. I think your question is something along the lines of "How is the spatial information in the light field encoded?". The answer to that would be "It's encoded in angles between light rays. Lenses can convert that angular information back into a spatial image.". Take the lenses away, and all the light that comes from other objects just makes a big blur. $\endgroup$
    – CuriousOne
    Oct 2, 2014 at 18:22

1 Answer 1


Your eye has a lens in it. Without a lens, the light is all spread out and overlapping, just like you say.

The light from any given pixel goes out in all directions, but a lens can make it re-converge back to a point.

Hold up a sheet of white paper. Is there an image on it? No, of course not. It has light on it---light coming from each object in the room---but no image. That's because there is no lens to make the image. I guess that's what you're imagining.

Eyes and cameras are special: They have lenses. Sharp images don't just form on their own.

  • $\begingroup$ OHhhhhh, duh... In my example used a camera adjusting itself to the light, why did I not remember that the eye is as much a camera obscura as a camera is. Now it seems so obvious!! Can't believe I couldn't work that out on my own. Thanks a million, I'm now reassured. Although, what I would not have thought up on my own is in regards to lenses. I learnt something new. $\endgroup$
    – Mallow
    Oct 3, 2014 at 14:57

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