Re: blackbody radiation

[John Denker <jsd@AV8N.COM>]

Justin Parke wrote:

> Imagine two boxes, one a "true"blackbody radiator (such as the box
> with aluminum foil referred to by John D.) and the other a collection
> of tunable lasers.  These lasers are tuned and have intensities in
> such a way that when someone plots the intensity verus wavelength of
> the light coming out of the box the resulting curve matches that of a
> blackbody.
>
> Now if a thermometer is used to measure the temperature inside the
> two boxes the temperature of the first box, the one with the "true"
> blackbody in it, will correspond to the peak wavelength according to
> Wien's law, whereas the second will not.
>
> This is an apparent paradox to me. What is wrong?

Not really a paradox.  There is one and only one blackbody
spectrum for any given temperature.  The Wien displacement
law is a _partial_ description of this spectrum.  Wien
tells us the shape but not the overall magnitude.  The
lasers would almost certainly be too bright;  right shape,
excessive magnitude.

The law that gives the complete description -- magnitude
as well as shape -- has Planck's name on it.
  http://www.nobel.se/physics/laureates/1918/press.html