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Question for the scientists amongst us.
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By (user no longer on site) OP
over a year ago
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When you open yer lounge door to go get another beer, some heat inevitably escapes from the room.
So, how much light escapes from the room, given that the hallway is unlit? |
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the area of the doorway divided by the total area of the room including the ceiling and the floor times the wattage of the bulb (s) ... so not much
whats faster the speed of light or the speed of dark |
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By (user no longer on site)
over a year ago
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Heat according to the parabolic partial differential equation.
Calling into use the Radiative transfer equation using diffuse reflectance for a pencil beam normally incident on a semi-infinite medium, I'd say it depends on the amount bouncing from the tops of the bald headed men in the room. |
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By (user no longer on site)
over a year ago
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I'm confused by the question.
It is suggesting that losing heat from a fixed space is easily comparable to light 'lost'.
The room doesn't get dimmer. The 'amount' of light, I.e brightness in the room doesn't change as there isn't a 'wave of darkness' from the unlit hallway entering the room you are leaving.
The light that would have illuminated the door just travels further, I.e into the corridor beyond the door you have opened. None of its effect on the room of origin is lost.
I suppose you can 'measure' a surrogate of light energy with a photometer. Calculate the average light intensity and multiple by the area exposed by door opening.
But I would ask you, why bother? |
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By (user no longer on site)
over a year ago
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"I'm confused by the question.
It is suggesting that losing heat from a fixed space is easily comparable to light 'lost'."
They're directly comparable aren't they? |
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By (user no longer on site) OP
over a year ago
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"I'm confused by the question.
It is suggesting that losing heat from a fixed space is easily comparable to light 'lost'.
The room doesn't get dimmer. The 'amount' of light, I.e brightness in the room doesn't change as there isn't a 'wave of darkness' from the unlit hallway entering the room you are leaving.
The light that would have illuminated the door just travels further, I.e into the corridor beyond the door you have opened. None of its effect on the room of origin is lost.
I suppose you can 'measure' a surrogate of light energy with a photometer. Calculate the average light intensity and multiple by the area exposed by door opening.
But I would ask you, why bother?"
Here, have a beer or two  |
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By (user no longer on site)
over a year ago
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"I'm confused by the question.
It is suggesting that losing heat from a fixed space is easily comparable to light 'lost'.
They're directly comparable aren't they?"
I didn't think so, because of the wording of the question. The way it is worded suggests equivalence between the way heat, insulated into a room is lost, and light, which is a stream of photons.
I don't see how opening a door reduces the stream of photons that traverse the room. I'm sure the effect of reflection is minimal. |
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By (user no longer on site)
over a year ago
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"
When you open yer lounge door to go get another beer, some heat inevitably escapes from the room.
So, how much light escapes from the room, given that the hallway is unlit? "
Omg at last a swinger who has lights x  |
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By (user no longer on site)
over a year ago
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Aaagh, but when you open the fridge door, can the fridge light reach the hall? If so, the room may lighten, marginally.
Hurry up with that beer - & can I've some asprin? |
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By (user no longer on site) OP
over a year ago
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"
I don't see how opening a door reduces the stream of photons that traverse the room. I'm sure the effect of reflection is minimal."
Are you suggesting that no photons leave the room at all? |
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By (user no longer on site)
over a year ago
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"I'm confused by the question.
It is suggesting that losing heat from a fixed space is easily comparable to light 'lost'.
The room doesn't get dimmer. The 'amount' of light, I.e brightness in the room doesn't change as there isn't a 'wave of darkness' from the unlit hallway entering the room you are leaving.
The light that would have illuminated the door just travels further, I.e into the corridor beyond the door you have opened. None of its effect on the room of origin is lost.
I suppose you can 'measure' a surrogate of light energy with a photometer. Calculate the average light intensity and multiple by the area exposed by door opening.
But I would ask you, why bother?"
Opening the door into a dark corridor will fractionally reduce the illumination in the main room. The light will no longer be reflected back into the room by the door and, as it escspes down the corridor, will lose intensity with the square of the distance.
This makes a change from look at me profiles. |
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By (user no longer on site)
over a year ago
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"I'm confused by the question.
It is suggesting that losing heat from a fixed space is easily comparable to light 'lost'.
The room doesn't get dimmer. The 'amount' of light, I.e brightness in the room doesn't change as there isn't a 'wave of darkness' from the unlit hallway entering the room you are leaving.
The light that would have illuminated the door just travels further, I.e into the corridor beyond the door you have opened. None of its effect on the room of origin is lost.
I suppose you can 'measure' a surrogate of light energy with a photometer. Calculate the average light intensity and multiple by the area exposed by door opening.
But I would ask you, why bother?
Opening the door into a dark corridor will fractionally reduce the illumination in the main room. The light will no longer be reflected back into the room by the door and, as it escspes down the corridor, will lose intensity with the square of the distance.
This makes a change from look at me profiles. "
Indeed, thanks for putting it so succinctly (been a while since I did any physics). The main perceivable loss within the room therefore would lost reflection rather than the intensity leaving the room? |
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By (user no longer on site)
over a year ago
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"
I don't see how opening a door reduces the stream of photons that traverse the room. I'm sure the effect of reflection is minimal.
Are you suggesting that no photons leave the room at all? "
I may be misspeaking, but in essence the photons are travelling in straight lines, with reflections here and there.
Heat is an integrated property of the matter within the room that behaves differently.
That was the main confusing point for me old chap. The kind sir above this post by a few kindly summarised things better.. |
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By (user no longer on site) OP
over a year ago
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"I don't go for beer, therefore none. Is that the right answer?"
It's modern General Science, any answer will do.
Unless your room is airtight, not a good thing, little bits of light will escape through the tiny gaps. Allegedly.
ps you've saved me a new thread, i was wondering where all the women scientists were.
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By *icketysplitsWoman
over a year ago
Way over Yonder, that's where I'm bound |
"I don't go for beer, therefore none. Is that the right answer?
It's modern General Science, any answer will do.
Unless your room is airtight, not a good thing, little bits of light will escape through the tiny gaps. Allegedly.
ps you've saved me a new thread, i was wondering where all the women scientists were.
"
It may have been the women in the couples responding.
This might be the subject of the Christmas Lectures so you will get your answer then.
I have low energy bulbs so they take ages before they give out any discernible light. On that basis, I keep the hallway light as well as the one in the living room. The hallway light seems to add more light to the living room but the living room adds nothing to the hallway.
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By (user no longer on site) OP
over a year ago
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"I don't go for beer, therefore none. Is that the right answer?
It's modern General Science, any answer will do.
Unless your room is airtight, not a good thing, little bits of light will escape through the tiny gaps. Allegedly.
ps you've saved me a new thread, i was wondering where all the women scientists were.
It may have been the women in the couples responding.
This might be the subject of the Christmas Lectures so you will get your answer then.
I have low energy bulbs so they take ages before they give out any discernible light. On that basis, I keep the hallway light as well as the one in the living room. The hallway light seems to add more light to the living room but the living room adds nothing to the hallway.
"
I see your problem, you've put the Male bulb in yer living room. |
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By *icketysplitsWoman
over a year ago
Way over Yonder, that's where I'm bound |
"But the door may be coloured matt black, in which case- almost zero reflection.
1 × beer & 2 x asprin, ta!"
I was wondering about doors with a curtain over them to keep the heat in. They should contain the light too.
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Take a reading with a light meter in the room with the light on. Take a reading in the hall with door shut, it won't be absolute darkness. With door opened, take a reading of the light level and subtract the original hall reading, this will give the amount of additional light now in the hall. Take this as a percentage of light in the lit room, that is how much light is getting out. Simples  |
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By (user no longer on site) OP
over a year ago
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"But the door may be coloured matt black, in which case- almost zero reflection.
1 × beer & 2 x asprin, ta!
I was wondering about doors with a curtain over them to keep the heat in. They should contain the light too.
"
You must've heard of blackout curtains? |
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By (user no longer on site)
over a year ago
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"Take a reading with a light meter in the room with the light on. Take a reading in the hall with door shut, it won't be absolute darkness. With door opened, take a reading of the light level and subtract the original hall reading, this will give the amount of additional light now in the hall. Take this as a percentage of light in the lit room, that is how much light is getting out. Simples "
But when you close the door there wouldn't be time to measure the light that had already got out. |
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By *icketysplitsWoman
over a year ago
Way over Yonder, that's where I'm bound |
"But the door may be coloured matt black, in which case- almost zero reflection.
1 × beer & 2 x asprin, ta!
I was wondering about doors with a curtain over them to keep the heat in. They should contain the light too.
You must've heard of blackout curtains?"
Indeed. But before I had central heating and I only had the one gas fire in the living room I would insulate that room with a curtain.
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By (user no longer on site) OP
over a year ago
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"Take a reading with a light meter in the room with the light on. Take a reading in the hall with door shut, it won't be absolute darkness. With door opened, take a reading of the light level and subtract the original hall reading, this will give the amount of additional light now in the hall. Take this as a percentage of light in the lit room, that is how much light is getting out. Simples "
Winner.
ahem, you don't have a light meter you could lend could yer  |
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By (user no longer on site)
over a year ago
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"The question in itself is incorrect. The light from the lit room would would have left before the door was opened?"
I think so. If not a room would just get brighter and brighter. |
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"Take a reading with a light meter in the room with the light on. Take a reading in the hall with door shut, it won't be absolute darkness. With door opened, take a reading of the light level and subtract the original hall reading, this will give the amount of additional light now in the hall. Take this as a percentage of light in the lit room, that is how much light is getting out. Simples
Winner.
ahem, you don't have a light meter you could lend could yer "
It's at work, |
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By (user no longer on site)
over a year ago
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Now the wine has taken effect I think the things proposed so far are flawed.
Light can't just reflect everywhere otherwise a light source would cause a room to get brighter and brighter. So it must also get absorbed (like heat).
A light meter (I think) measures available light - not quantity of light. So it wouldn't work to calculate the amount of light lost when a door is opened.
I think you would need some sort of reflective bucket thing that could capture the light and stop it being absorbed and prevent leaks in order for it to be calculated.
Alternatively maybe each time we open a door we create a short lived star for people on another world.. |
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"Now the wine has taken effect I think the things proposed so far are flawed.
Light can't just reflect everywhere otherwise a light source would cause a room to get brighter and brighter. So it must also get absorbed (like heat).
A light meter (I think) measures available light - not quantity of light. So it wouldn't work to calculate the amount of light lost when a door is opened.
I think you would need some sort of reflective bucket thing that could capture the light and stop it being absorbed and prevent leaks in order for it to be calculated.
Alternatively maybe each time we open a door we create a short lived star for people on another world.."
See, and they laughed at me when I tried to patent my "light bucket" ffs!  |
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By *icketysplitsWoman
over a year ago
Way over Yonder, that's where I'm bound |
"Doh - light bucket. It's always the obvious thing in the end
Sod off, I invented it first! "
Does the light live in the bucket or do you just trap excess light in the bucket to take it somewhere else? |
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