Tough question to articulate, but hopefully very answerable.
Presumably, from whatever angle imaginable away from your hand, as an example, there is information in the form of [light waves?] about the shape and color of your hand, but that information only becomes relevant from your unique perspective. “Directly” let’s say. You can’t see the “data”/lightwaves being sent in every other possible direction away from the hand, even though no matter where you are in the room, assuming nothing obscures your view, you could see the hand.
In: Physics
I think what you’re getting at is the concept of a “diffuse” reflection.
Then image of your hand is being sent of in every direction, but most surfaces are too rough to meaningfully reflect that image back into your eye. The light falls on nearby walls and surfaces and is randomly scattered to produce a new image of whatever it hit.
You can view this indirect “virtual” image in a mirror, which reflects light back at the same angle it came in at instead of at a random angle.
Because it *doesn’t* scatter much light, you can’t actually look at the mirror itself (the backing is aluminum and the glass is faintly green) very easily – only the reflected image that overwhelms it.
They aren’t seen going in every direction because you can only see what hits your eyes, and your eyes are only hit by the light coming directly at you.
You can prove that light is being sent in every direction by simply setting a mirror some distance away from your hand. You’ll be able to see your hand in the mirror; therefore, light *is* heading in every direction.
Because our eye can only see light that hits it.
Saw this comparison in a similar thread and it makes a lot of sense:
Imagine you have food in front of you. Now pick it up and move it into your mouth so you can eat it – do you gain nutrition from that food that *entered your mouth*? Yes (assuming it had nutrition to offer).
Now take that same food, and move it past your head without letting it into your mouth – do you gain nutrition from that food *not* entering your mouth? No.
Your eyes work similarly, they only react to light that enters the eye and do not react to light traveling on a path that doesn’t enter your eye. A glowing object is different in that it continuously emits light that *does* hit your eye as it travels…but individual light photons do not emit more light photons in all directions.
To give some extra context, imagine laser pointers.
Normally you can only see the spot on whatever surface you shine it on, and MAYBE a small bit of the beam as it hits bits of dust or something floating around. For the most part, because they are such direct beams of light, there is no light to enter your eyes.
Now, imagine you shine it through fog or smoke. That puts a lot more into the air for it to bounce off of, just like in those scenes in heist or spy movies, where they spray stuff to make laser grids visible.
Now, once you get strong enough lasers, or maybe lasers of a specific type, I’m not sure of the specifics, then you start to have beams that are just always visible. A lot of these are gonna be like those high powered burning lasers you see on things like Styropyro videos. They put out enough power that just looking at the spot on the wall, much less getting hit with the actual beam can cause permanent eye damage.
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