Re: Hole in a box

From: Mike Lorrey (
Date: Sat Feb 16 2002 - 08:04:59 MST

John Clark wrote:
> Mike Lorrey <> Wrote:
> >Since large quantities of hard radiation pass right through objects,
> >that which passes thru obviously doesn't impart any energy, so your
> >efficiency relative to total flux drops as frequency rises.
> The reason Black Holes produce X rays at all is because there is
> a accretion disk of gas around it that is heated to millions of degrees
> just before it falls into the hole, the enormous tidal forces compress
> the gas and makes it hot, great stuff for a heat engine.
> Another example is the H bomb, a fission trigger produces X rays and
> heats some plastic foam to millions of degrees and compresses the fusion
> materials. X rays are not neutrinos, lots of things absorb them including air.

Saying a material 'absorbs x-rays' is a rather vacuous statement. What
PERCENT of xrays are absorbed for a given thickness/density of matter?
It doesn't matter if the foam in an h-bomb is heated to millions of
degrees. If the foam only catches 1% of the xrays to do that work, then
it has, at best, a 1% efficiency. Then what percent of that 1% is
actually doing real work? In the case, for example, of a photovoltaic
unit, it absorbs nearly 100% of the visible spectrum (some blue is
reflected/reemitted) yet converts only 10-30% of that amount to
electricity. No light passes through a PV unit of a given thickness.

With x-rays, you will get x% of the radiation passing straight through
the material with no influence whatsoever. The material WILL absorb the
rest, converting the energy into heat, electicity, and other means of
dissipation, but if your goal is getting electricity out of absorbing
x-rays, it is only the percent of xrays that produce electricity that
account for your efficiency. The fact that xray radiation has such a
high pass-thru ratio for a given amount of mass, compared to lower
frequencies, makes it less than ideal as a source for power generation.

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