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sci-man

sphere and light

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if someone were to create a perfect-ish hollow sphere that was about a foot wide and was super reflective on the inside and they put a light like an led bulb or something inside of it then closed it what would happen?

my hypothesis is that there would be a lot of heat with the light bouncing around so much. 

what would happen if you increased the size or decreased the size of the sphere its self including the size of the hollow area inside?

thanks for reading and thanks if you comment too!

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Hi, sci-man. You have brought an interesting and essential theme. In the situation that you pose there are variables that determine the possible events. For example, the spectrum of the light source located within the sphere, whose components are comprised between a minimum frequency (related to the size of the enclosure) and a maximum frequency (related to differences between the quantum levels responsible for providing quotas of energy used to accelerate electrons).

The values taken by the variables in the source of EM radiation determine the sequence of events. A set of values can produce, as you said, a thermal equilibrium within the enclosure. Another set of values can produce standing waves that fill the whole volume without generating heat, that is, standing waves that oscillate monotonously without entropy variation. Another set of values can trigger the formation of particle and antiparticle pairs. The different possibilities are numerous.

Can there be something on the Internet that works for you, maybe something like the following links?

users.df.uba.ar/arbo/PhotonGasAJP.pdf

www.physics.udel.edu/~glyde/PHYS813/Lectures/chapter_7.pdf

physics.ucsc.edu/~drip/5D/photons/photons.pdf

https://arxiv.org/pdf/1708.09524

https://www.americanlaboratory.com/342125-Fast-Quantum-Memory-Stores-Photons-in-Gas-of-Rubidium-Atoms/

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On 01/10/2018 at 1:33 PM, sci-man said:

if someone were to create a perfect-ish hollow sphere that was about a foot wide and was super reflective on the inside and they put a light like an led bulb or something inside of it then closed it what would happen?

my hypothesis is that there would be a lot of heat with the light bouncing around so much. 

what would happen if you increased the size or decreased the size of the sphere its self including the size of the hollow area inside?

thanks for reading and thanks if you comment too!

Indeed the globe would get hotter and hotter and might even burst into flames.

This is not suprising.

This is exactly what happened to early LED ceiling downlighters because someone didn't realise that if you keep pumping energy into an enclosed space it will heat up.

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On 10/1/2018 at 8:33 AM, sci-man said:

if someone were to create a perfect-ish hollow sphere that was about a foot wide and was super reflective on the inside and they put a light like an led bulb or something inside of it then closed it what would happen?

my hypothesis is that there would be a lot of heat with the light bouncing around so much. 

These are inversely correlated. The more the light bounces around, the more slowly it will heat up. It's the loss of photons from not bouncing around that will raise the temperature.

In reality, though, the bouncing of any pulse will effectively cease in a fraction of a second.

The power output of the system would match the LED once you reach steady state — energy is conserved. However, depending on the properties of the material, the temperature might rise somewhat before that happens — radiated energy varies as T^4, so a small temperature increase goes a long way.

On 10/1/2018 at 8:33 AM, sci-man said:

what would happen if you increased the size or decreased the size of the sphere its self including the size of the hollow area inside?

thanks for reading and thanks if you comment too!

That raises the time in between bounces. But even a super mirror, with 0.9999 reflection, will drop the intensity to about half of original after ~7000 bounces. And c is 3 x 10^8 m/s, so even if these surfaces are, on average, a meter apart, that takes ~23 microseconds (or ~3 times faster for a foot apart)

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47 minutes ago, sci-man said:

so this would not work then?

or it wont be as powerful as i hoped

 

What wouldn't work?

 

You guessed what would happen if you put a light source inside a reflective globe and asked if you were right.

We largely agreed with you.

 

But there didn't seem to be any purpose to the contraption.

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The proposed sphere's size in comparison to the proposed heat source, an LED, might not yield anything at all, insofar as spectacular results are concerned. LEDs generate but little heat themselves. However, be aware that light fixtures now sold for use in everyday lighting may contain heat-producing circuitry utilized to successfully operate LEDs on "household current". This is especially true of CFLs (Coiled Fluorescent Lamps) which contain some mysterious "ballasting" which becomes quite hot. This is mentioned in reference to the remark about overhead fixtures.

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