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reemissionFrom: Steven
Subject: Philosophy
Date/Time 2009-06-16 21:48:55
Remote IP: 74.235.102.47
Message>>>One question though, don't luminesants produce certain chemicals
>>>to create the light they emit?....Do they still have to gather
>>>light to reemit it or is it the chemicals produced that becomes an independent >>>light source?
Oftentimes it is an electrochemical response. Due to certain types
of chemical reactions, the products of these reactions often produce
molecules that naturally have a lower stable energy. The extra energy
therefore is given off in a deexcitation process. Oftentimes this
extra energy is given off in the form of heat, but sometimes it is
given off as light [actually both heat and light are both just forms
of EM radiation]. If an object is emitting more visible light than
what it is receiving, then that energy has to come from somewhere.
In the case of fireflys, say, it is an electrochemical response.
In the case of a red hot poker, it is the temperature difference.
>>>Also does something have to be mirrored to reflect light ?
>>>I thought that if light hit an object and couldn't pass
>>>through it it was reflected back in a different direction
>>>and that is what our eye's pick up in order to see what
>>>is in front of them.
To be perfectly, perfectly honest, even a mirror doesn't really
reflect light. That's an early idea of Isaac's Newton's when
people were first trying to understand light. However, with a mirror
the reemission is so damn near perfectly identical to what is
striking it, that you may as well call it reflection. In the case
of a mirror, you will never really get into any problems pretending
that light is "reflecting". This really can *not* be said
of other objects however. In these cases, the light that is
reemitted is drastically different from what is striking it.
For instance, it is very difficult to get a good understanding
of the nature of color if you don't treat light interaction as
it actually happens (that is, the full spectrum of light strikes
a non-transparent object, the object absorbs the whole spectrum and
absorbs all of it, then the object through a deexcitation process
emits its own spectrum--sometimes completely different from what
was incident).
The more accurate description of what is going on is what is necessary
to understand "apparent paradoxes" such as "white light is
the sum of all colors as seen from a prism" but "mixing all colors of
paint in a can yields black".
S
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