Scattering of light inside a room

[Pushoam]

TL;DR Summary

Using the sun as a light source, why do we experience the presence of light in a room with open windows even when direct sunlight is not coming to the room?

Using the sun as a light source, why do we experience the presence of light in a room with open windows even when direct sunlight is not coming to the room?
A possible explanation:
We don't see the light in the room, yet we experience it.
A part of the atmosphere is present in the room. The atmospheric particles scatter the visible light and the scattered light enter our eyes and hence, we experience presence of light.

Now, if the particles scatter the visible light, why are we not able to see the particles?
Why does the part of the atmosphere present in the room appear transparent? And if these particles are really transparent, then why don't we experience darkness as we will do in case of vacuum(which is 100% transparent)?
Could anyone please explain the scattering of light occurring in the room because of which we neither see the atmospheric particles nor experience the darkness?

 

[russ_watters]

The light is reflecting (diffuse) off every surface in the room. It is not being scattered by particles suspended in the air (that's fog).

 

[Pushoam]

The light is reflecting (diffuse) off every surface in the room. It is not being scattered by particles suspended in the air (that's fog).

Do you mean that the walls of the room reflect the light and we experience that light?
In this case, we see the colour of the wall. I am talking of the space between the walls. This space doesn't appear dark to us. So, some light does enter the eye. Although, I don't see any colour of the light.
Another explanation:
The light which I experience is the light reflected by the objects in the room, not the light scattered by the atmospheric particles in the room. Then, in this case, if all objects in the room are black coloured, then I should experience the darkness. But, this doesn't happen. Even if all the objects are black in colour, I do experience light.

Besides, I experience the presence of light under the sky, where there is no object (except atmospheric particles) to reflect the light.

 

[russ_watters]

Do you mean that the walls of the room reflect the light and we experience that light?

"Experience" is a strange word choice. We see light.

In this case, we see the colour of the wall. I am talking of the space between the walls. This space doesn't appear dark to us.

No, that space doesn't appear anything to us. It is transparent.

Then, in this case, if all objects in the room are black coloured, then I should experience the darkness. But, this doesn't happen. Even if all the objects are black in colour, I do experience light.

Most of what we consider black is not very black. Google "blackest paint" and look at some of the pictures. It's pretty wild.

Besides, I experience the presence of light under the sky, where there is no object (except atmospheric particles) to reflect the light.

The sky does in fact scatter sunlight. That's why it is blue. But this does not happen enough to see near you, it is happening many km away.

 

[Dale]

TL;DR Summary: Using the sun as a light source, why do we experience the presence of light in a room with open windows even when direct sunlight is not coming to the room?

Using the sun as a light source, why do we experience the presence of light in a room with open windows even when direct sunlight is not coming to the room?
A possible explanation:
We don't see the light in the room, yet we experience it.
A part of the atmosphere is present in the room. The atmospheric particles scatter the visible light and the scattered light enter our eyes and hence, we experience presence of light.

Now, if the particles scatter the visible light, why are we not able to see the particles?
Why does the part of the atmosphere present in the room appear transparent? And if these particles are really transparent, then why don't we experience darkness as we will do in case of vacuum(which is 100% transparent)?
Could anyone please explain the scattering of light occurring in the room because of which we neither see the atmospheric particles nor experience the darkness?

It is typically not scattering in the atmosphere, but reflection off the other surfaces that are visible outside the window. E.g. there is a tree outside your window, the sunlight hits the tree and reflects into the room, brightening the room.

 

[Pushoam]

No, that space doesn't appear anything to us. It is transparent.

Yes, but looking at this space we can say whether there is light or not.
Vacuum is transparent. And if instead of atmospheric particles, we have vacuum inside the room, then the space will appear dark. The space doesn't appear dark. This implies that the atmospheric particles do scatter visible light.

The sky appears blue because of the scattering of light due to atmospheric particles. That means atmospheric particles do scatter the visible light. The atmospheric particles are present in the room, too. So, they do scatter light and the scattered light reaches our light and we experience presence of light.

 

[berkeman]

And if instead of atmospheric particles, we have vacuum inside the room, then the space will appear dark.

Not if the room has windows...

 

[Pushoam]

Not if the room has windows...

Yes, the window is closed in this case and we can take a source of light inside the room.

 

[berkeman]

Then the source of light is lighting the room. It makes no difference if there is air or not. That much air is transparent to light.

 

[Dale]

we experience the presence of light in a room with open windows even when direct sunlight is not coming to the room?

Yes, the window is closed in this case and we can take a source of light inside the room.

Please do not change the topic. That is confusing. This thread, as started by you, is about a room with an open window.

 

[Pushoam]

The sky appears blue because of the scattering of light due to atmospheric particles. That means atmospheric particles do scatter the visible light. The atmospheric particles are present in the room, too. So, they do scatter light and the scattered light reaches our light and we experience presence of light.

Is this part correct?

 

[russ_watters]

Yes, but looking at this space we can say whether there is light or not.

No, you cannot "look at this space" if it is not reflecting light.

And if instead of atmospheric particles, we have vacuum inside the room, then the space will appear dark. The space doesn't appear dark. This implies that the atmospheric particles do scatter visible light.

No. That's totally wrong. Space, as in outer space, looks black because there is nothing in or around it reflecting light. An astronaut on the moon looks at the moon and it is bright. Then he looks at the "sky"/space and sees nothing else. But when he's in his spaceship (with a window to let sunlight in), he can look all around him and see....the inside of the spaceship (whether the hatch is open/ closed and it has air in it or not). When you are in your room, you are looking at the inside of the room, not the air.

The sky appears blue because of the scattering of light due to atmospheric particles. That means atmospheric particles do scatter the visible light. The atmospheric particles are present in the room, too. So, they do scatter light and the scattered light reaches our light and we experience presence of light.

Read the rest of what I wrote. This is not a local phenomenon. It happens many km away. It is not detectable in your room and in either case, your room doesn't look blue, does it?

 

[russ_watters]

Is this part correct?

No. Is your room blue/can you see a blue fog in front of you?

 

[Pushoam]

Please do not change the topic. That is confusing. This thread, as started by you, is about a room with an open window.

I am trying to understand our experience of presence of light in the space between two walls of a room.
Here, I learnt that the light reflected from different objects e.g. tree or building reaches the room
and makes things visible in the room. The reflected light either from the outside objects e.g. tree o r the inside objects e.g. walls of the room reaches eye and I am able to see the objects and feel the presence of the light. The space between the two objects is transparent and it does contain light. Is this correct?
Now , the question is why don't we experience the scattered light due to atmospheric particles in the room?

 

[hutchphd]

Now , the question is why don't we experience the scattered light due to atmospheric particles in the room?

Because this scattering is very very very slight, compared with everything else in the room that is scattering light.

 

[Pushoam]

Thank you, all.
Now, I understood it.

 

[Pushoam]

Is your room blue/can you see a blue fog in front of you?

The room does not appear blue because the amount of blue light scattered by the atmospheric particles in the room is too low to be experienced by a naked eye.
The room not appearing blue does not rule out the scattering of light due to atmospheric particles inside the room.

 

[Dale]

I am trying to understand our experience of presence of light in the space between two walls of a room.
Here, I learnt that the light reflected from different objects e.g. tree or building reaches the room
and makes things visible in the room. The reflected light either from the outside objects e.g. tree o r the inside objects e.g. walls of the room reaches eye and I am able to see the objects and feel the presence of the light. The space between the two objects is transparent and it does contain light. Is this correct?

Yes, that is correct.

Now , the question is why don't we experience the scattered light due to atmospheric particles in the room?

The atmosphere is very transparent to visible light. It scatters it very little. Light must pass through many kilometers of air for there to be any significant scattering, and even then it is typically only blue light that gets scattered. So the reason is simply that you do not have many kilometers of air in the room.

 

[Pushoam]

Thank you.

 

[hmmm27]

 

[DeBangis21]

It is typically not scattering in the atmosphere, but reflection off the other surfaces that are visible outside the window. E.g. there is a tree outside your window, the sunlight hits the tree and reflects into the room, brightening the room.

Exactly in my case, there's a big tree outside the windows. During sunrise, my whole room lights up.

 

[hutchphd]

You have to have many kilometers of light for there to be any significant scattering, and even then it is typically only blue light that gets scattered.

The number I carry in my head for Rayleigh Scattering (~500nm blue) in STP air is 1% scattered per km). I like to know some numbers

 

[russ_watters]

[world's blackest paint video]

Ow, my nose!