I was thinking about light, and then I realized that if light is travelling in all directions form all sources (either emitted or reflected) everything should be merged together in a big light blob.

Take this illustration of light:

enter image description here

As you can see, light from the top of the head is reaching both the top and bottom of the eye. And the same goes for the toes, where light reaches both the top and bottom of the eye at the same time. As a particle/wave of brown from the top of the head is reaching the eye at the same time as the green shoes, shouldn't we be seeing something different from a clear image?

This can also be seen in a photo, if the light from the toes reaches the lens at the same time that the light from the hair does, they should be mixed. If the light is emanating from the source as a stream of particles, we should be seeing a massive light that changes color as the light reaches us at different times due to slight difference in distance.


You're absolutely correct, that is exactly why you have a lens in your eye and why imaging systems use lenses. A lens knows to focus all of the light coming from a point back to a single point, thus cancelling the blur effect you described.

However, if you're not exactly in the imaging plane, you do see a blur.

  • $\begingroup$ But, what if the light particle from the top of the head reaches this single point at the same time as a light particle from the bottom of the shoes? Both particles are reaching the same point, which the lens focuses. but if they are at the same point, what are we seeing? $\endgroup$ – Matthew Mar 16 '17 at 23:36
  • $\begingroup$ Can you clarify your question? $\endgroup$ – Ofek Gillon Mar 16 '17 at 23:38
  • $\begingroup$ I think I am getting this now... Is what is happening is that even though there is light all around us traveling in many directions, but the lens is taking a single infinite point and just allowing that light to carry the color? Maybe I need to research more on lenses... $\endgroup$ – Matthew Mar 16 '17 at 23:49
  • $\begingroup$ I am seeing this: en.wikipedia.org/wiki/Camera_lens - I think it is helping to understand as well. $\endgroup$ – Matthew Mar 16 '17 at 23:54
  • 1
    $\begingroup$ Great, you should watch this too: youtube.com/watch?v=OydqR_7_DjI $\endgroup$ – Ofek Gillon Mar 16 '17 at 23:56

Light doesn't reach us from all the directions. It comes to us from an object that produces light or an object that reflects light that it had received from some other source. That's why, when you are locked in a closed room with no light source, nothing will glow.

  • $\begingroup$ I think you miss the point of the question. See Ofek Gillon's answer. $\endgroup$ – Floris Mar 17 '17 at 0:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.