Propagation speed...

[Externet]

What is the propagation speed of radiant heat?

[ydoaPs]

c(speed of light)

[Externet]

OK, thanks.

So it is an electromagnetic wave.

As in distant atomic bomb explosions, photons from the flash are perceived simoultaneously with the heat; the shock wave and noise is obviously later.

[ydoaPs]

yes

[swansont]

OK' date=' thanks.

So it is an electromagnetic wave.

As in distant atomic bomb explosions, photons from the flash are perceived simoultaneously with the heat; the shock wave and noise is obviously later.[/quote']

 

You shouldn't distinguish between the photons and the radiant heat. They are the same thing.

[[Tycho?]]

OK' date=' thanks.

So it is an electromagnetic wave.

As in distant atomic bomb explosions, photons from the flash are perceived simoultaneously with the heat; the shock wave and noise is obviously later.[/quote']

 

Radiant heat is EM radiation, so its made up as photons just like light and x-rays.

[Externet]

Oh, boy !

Thanks.-

 

By Swansont : ...You shouldn't distinguish between the photons and the radiant heat. They are the same thing."...

 

By Tycho? : ...Radiant heat is EM radiation, so its made up as photons just like light and x-rays.

 

Both opinions on the same track... perhaps am influenced by the word 'photons' I thought being visible-only light emitting... which is not visible in far infrared (heat) radiation; but still named photons ?

 

OK; next step. ¿What would it take to make a solar cell with shifted response towards the far infrared spectrum; if it is a photon emission, could dislodge electrons from a PN junction and create some electrical current when exposed to radiated heat ?

 

Miguel

[insane_alien]

solar cells won't work. waaaaay too low energies. i can't remember the name of the sensors used for IR but i think they need to be kept very cold for some reason.

[Externet]

Agreed, solar cells do not work with heat radiation. That is the point.

 

Rephrasing... What would take to make a cell similar to solar but centered in the far IR ? -- "thermovoltaic" instead of photovoltaic --

 

It is not about sensors, as the ones used in infrared cameras and thermal imaging, those are fine for detection but not for generation.

 

What does waaaay too low energy refers to ? The heat radiation to be collected or the electrovalence energyband something of the PN junction ?

 

Miguel

[5614]

All electromagnetic radiation is photons. That's:

radio waves

micro waves

infrared

visible light

ultra violet

x-rays

gamma rays

... they're all photons. Just at differnet frequencies (highest at the bottom of that list) and wavelengths (highest at the top of that list).

 

IR photons do not have enough energy to knock electrons off in solar cells. You can see why because the energy of a photon is given as:

E = hf

E is energy

h is Planck's constant, simply put it's just a constant

f is frequency

so clearly the higher the frequency the more energy. Now IR has quite a low frequency and so it has low energy. It's energy is so low it cannot be used in solar cells.

[swansont]

Oh' date=' boy !

Thanks.-

 

By Swansont : ...You shouldn't distinguish between the photons and the radiant heat. They are the same thing."...

 

By Tycho? : ...Radiant heat is EM radiation, so its made up as photons just like light and x-rays.

 

Both opinions on the same track... perhaps am influenced by the word 'photons' I thought being visible-only light emitting... which is not visible in far infrared (heat) radiation; but still named photons ?

[/quote']

 

 

IR is not synonymous with heat, though. You can radiate energy using any wavelength; you can e.g. heat things radiatively with a microwave oven and with a visible-light laser, with no IR at the source.

 

For objects at temperatures we are used to seeing, much of the radiation is in the IR. But all of the radiation is heat.

[Externet]

Thanks, gentlemen; am learning good from you.

 

If all energy are photons, visible light range or radio range, the point of view can be changed from visible light spectrum to radio spectrum.

 

As ..."IR has quite a low frequency and so it has low energy"...

 

Focusing the center of attention to radiowaves (also photon EM energy) ; the IR spectrum has a MUCH higher frequency and higher energy than radio.

 

Trying to express myself better:

 

A plain microwave oven, rated say 1 Kw emits EM photons at 4 GHz. If its frequency is increased (towards IR) the energy emission would be greater (am not talking about its cooking abilities) as :

 

"E = hf

E is energy

h is Planck's constant, simply put it's just a constant

f is frequency"

 

Then the new rephrasing would be... ¿How to manufacture a PN junction cell of some kind that will convert RF into an electric current and performing up to IR ?

 

Is the explanation still the same -too low energy- ?

If so, that 1Kw ! microwave oven is too little energy to recover any from its confined chamber by means of some sort of cell ?

 

Thanks,

Miguel

[insane_alien]

microwave ovens use 2.4GHz it heats the water best. the greater the wattage the greater the intensity in this case.

[5614]

So you think your powerful microwave should be able to activate a solar cell? But it can't, and the reason is quite simple yet clever.

 

Both mine (weak) and your (powerful) microwave emit microwaves at the same frequency. Therefore each individual photon in both of our microwaves have the same energy. Why then is yours more powerful? Because it makes more photons.

 

Each of your photons have the same amount of energy as mine. But like IR photons they do not have sufficient energy to knock an electron off. The fact that you have a lot of photons makes no difference. To knock an electron off you need one big shove (ie. lots of energy, high frequency), lots and lots of little shoves will never do anything.

 

Think about trying to push a man off a cliff who will do his best not to fall... even if you push him a million times with your baby finger he will never fall, because you are not supplying enough energy per push. But one big shove and he'll go.

 

Many photons (from a more powerful microwave) is just like many little pushes, none of them are big enough to knock the electron off, just as your baby finger will never push a man off a cliff. But one big, high energy, high frequency photon is enough to knock the electron off, likewise with the man and the cliff.

[swansont]

Then the new rephrasing would be... ¿How to manufacture a PN junction cell of some kind that will convert RF into an electric current and performing up to IR ?

 

Is the explanation still the same -too low energy- ?

If so' date=' that 1Kw ! microwave oven is too little energy to recover any from its confined chamber by means of some sort of cell ?

[/quote']

 

 

Try using an antenna instead. If you want DC, you add a rectifier, making it a rectenna

[Externet]

Thanks gentlemen; that was very clear, simply better than some text books.

 

The rectenna would be what am after, but in semiconductor style construction, perhaps using materials with the property that weak photons can knock their electrons off.

 

Miguel:-)