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Suppose it is dark. If someone shines a flashlight directly at you, you see light. If, however, someone shines a flashlight at something else, you see that thing illuminated, but you don't see the light beam of the flashlight traveling from the flashlight to the object.

Why, then, when I turn on a light in a dark room does everything seem light? It seems as though I can see the light traveling from the light bulb to all the corners of the room.

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    $\begingroup$ I have no idea what you are asking here. Different wavelengths do not interfere, and I don't know what "if you have light and you look at it under a 90 degree angle you see no light." is supposed to mean. $\endgroup$ – ACuriousMind Apr 11 '15 at 17:02
  • $\begingroup$ I think I understood the question - are my edits helpful? $\endgroup$ – innisfree Apr 11 '15 at 18:09
  • $\begingroup$ Possible duplicate of Why is light invisible? $\endgroup$ – Emilio Pisanty Feb 1 '18 at 10:03
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Assuming I've understood your question correctly:

The light from a bulb travels outwards in all directions and so hits (almost) all of the room. When it hits the walls etc, it gets reflected off of them (in most directions away from the wall), and then enters your eye. Hence your eye receives light from most of the room, so the room appears light.

It's important to emphasise that you don't see light travelling from the bulb to the wall. Light must enter your eye for you to see anything.

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I think I get what you are asking. see you are seeing the Light it self. this works like this:

Light consists of particles named photons. Atoms, all the time, are shooting photons out. But our eyes are only sensible to some of them. So it works like this, an objects atoms get to "excited state" and that is because they shoot out photons. When we observed these shot photons, we call this "seeing" .

You can not see the light. When you look at the lamp, you are not seeing the light. You are actually seeing a very hot metal. When the metal inside the lamp gets very hot, it shoots photons out. That is what you are seeing when you look at a lamp.

About other objects: when certain photons hit to the normal atoms it makes them "excited" . so they again shoot photons out. and when you are seeing other objects using the lamp, you are observing those photons.

So you do not see the photons. Our body uses the observed photons to create a picture of outside. But you can not see a photon, or as you say light. So all we see is the photons that been shot from atoms (when we get those kind of photons, we say we are seeing that object), not the photons itselves.

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We don't actually see light. The visible light spectrum is not light we can see. ( Since this narrow band of wavelengths is the means by which humans see, we refer to it as the visible light spectrum.) It doesn't matter if an object emits or reflects light, as long as our eyes detect light coming from an object, the object becomes visible to us. When someone shines a torch at you, you see the element in the globe. If they shine the light on an object, the object reflects light, we see the object. Light can even illuminate dust in it's path and we see a path of brighter dust. Our eyes detect light, that's true. But detecting light is just a part of the visual system. The end result, is vision. This is what gives humans an evolutionary advantage. Vision allows us to see predators, food and possible mates.

When you turn on the light, light strikes objects all around the room. Those objects reflect light into our eyes and we see those objects. Not light. We comprehend that there is light. But we don't perceive light.

Source http://www.physicsclassroom.com/class/light/Lesson-2/The-Electromagnetic-and-Visible-Spectra

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