Inverse Square Law

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Jason
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Inverse Square Law

Post by Jason » Thu Jan 24, 2013 7:11 pm

Just a quick question here.

The intensity of light per square unit is subject to the inverse square law in which the intensity can be estimated by the formula 1/x2 where x is the distance from the source. So an object 3 feet away from the source will receive 1/9th the light intensity that an object 1 foot away would.

My question is does this also apply to thermal energy? It seems to me that it sound as it is simply a longer wavelength.

Follow-up question can this be applied to convection through a medium, such as water, channeled through a hose?

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Re: Inverse Square Law

Post by Jason » Thu Jan 24, 2013 7:43 pm

Never mind, I found it. Good old Fourier. Clever bastard.

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Re: Inverse Square Law

Post by Jason » Thu Jan 24, 2013 7:51 pm

Then again.. maybe Newton's law of cooling is more applicable here.

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Re: Inverse Square Law

Post by Jason » Thu Jan 24, 2013 8:09 pm

Thermodynamics.. fluid dynamics.. Grashof numbers.. This is a lot more complex than I thought it would be.

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Re: Inverse Square Law

Post by cronus » Thu Jan 24, 2013 8:27 pm

I stopped at Laplace transforms and didn't go any further.
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Re: Inverse Square Law

Post by FBM » Thu Jan 24, 2013 8:28 pm

Yes. You're welcome. Please come again.
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Re: Inverse Square Law

Post by Jason » Thu Jan 24, 2013 8:35 pm

I'm just thinking aloud. It's surprisingly difficult and I'd hoped someone would have solved this problem before. :teef:

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Re: Inverse Square Law

Post by FBM » Thu Jan 24, 2013 8:40 pm

Făkünamę wrote:I'm just thinking aloud. It's surprisingly difficult and I'd hoped someone would have solved this problem before. :teef:
After a bit of searching, I found the solution here.
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Re: Inverse Square Law

Post by Jason » Thu Jan 24, 2013 8:44 pm

:bored:

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Re: Inverse Square Law

Post by Jason » Thu Jan 24, 2013 8:47 pm

I'm going to give up for now and hope some physics wiz will come along and help. It's now afternoon so I can drink.

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Re: Inverse Square Law

Post by JimC » Sun Jan 27, 2013 8:29 am

Făkünamę wrote:Just a quick question here.

The intensity of light per square unit is subject to the inverse square law in which the intensity can be estimated by the formula 1/x2 where x is the distance from the source. So an object 3 feet away from the source will receive 1/9th the light intensity that an object 1 foot away would.

My question is does this also apply to thermal energy? It seems to me that it sound as it is simply a longer wavelength.

Follow-up question can this be applied to convection through a medium, such as water, channeled through a hose?
It applies to any form of radiation from a point source, so heat radiation, sound etc. are all fine.

The rate of heat conduction through a given medium with a constant cross-section is directly proportional to both the length of the medium and the temperature differential, inversely proportional to the cross-sectional area, and also influenced by the heat conductivity of the medium.
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