Re: Hole in a box

From: Mike Lorrey (
Date: Thu Feb 14 2002 - 10:47:13 MST

Anders Sandberg wrote:
> On Thu, Feb 14, 2002 at 02:46:03PM +0100, Eugene Leitl wrote:
> >
> > Problem with small holes is that there's a tradeoff between luminosity and
> > blackbody wavelength. E.g. a 10 kK hole would radiate less than a 10 MK
> > hole, but 10 kK radiation sans attenuation would be a lot easier to use
> > with solid state photovoltaic devices.
> Thermodynamically speaking, wouldn't higher frequencies be more
> efficient? We have spent most work on photovoltaics at wavelengths close
> to solar radiation, but I don't see why similar ideas can't be used for
> higher frequencies. Hmm, beyond a certain range molecular matter of
> course becomes rather fragile, but there might be some interesting
> nuclear photovoltaics that catch gammas and use them to do charge
> separation.

Well, I'd have to say that higher frequencies would penetrate materials
deeper (i.e. x-rays, etc) so that a given receiver would necessarily
have a lower energy density to efficiency ratio. Microwaves, which are
longer wavelengths than visible light, can be rectified into electricity
at a much higher efficiency than visible light can, etc..

So you have this curve of wavelength conversion efficiency to deal with,
plus a curve of wavelength versus total flux. Where these two meet
should be the wavelength you want your black hole to produce the most

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