Re: gEDA-user: Plastic Ball Grid Array (PBGA) packages?

[Evan Lavelle <anti.spam1@xxxxxxxxxxxxx>]

M. P. Dickens wrote:

> Dark IR is nothing more than ir energy that is not visable to
> the human eye. For instance, IR heat lamps used to heat food are
> red. OTOH, ceramic fixtures and bulbs made of ceramic emit ir
> energy without producing any (Or very few) photons.
>  > Karel Kulhavy wrote:
>
> > What is dark IR? I know what IR is but don't know what a dark IR is.

<pedant>
IR is 'dark' by definition, in exactly the same way that a radio 
transmitter is 'dark'; that's what the 'I' means ('Infra' = 'under'-red; 
radio is even further 'under'-red). IR photons have an energy which is 
just less than, ie. a wavelength which is just longer than, the bottom 
end of the visible spectrum (ie. 'red' photons). IR lamps heat by 
radiation, ie. emitting photons.

Most IR sources will be spectrally impure; in other words, they will 
emit photons with a wide range of energies, including 'red' ones.
</pedant>