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Re: [Phys-l] Is light pure energy?



Feybnman's words provide a description of a calculation. They are not the calculation. As long as they lead to the correct calculation, it matters not that he has not led you to a cariety of other possible calculations.
I suggest viewing the words as a sort of poetry, the mathematics carries the essence of the physics.
Regards,
Jack



On Tue, 3 Jul 2007, Bernard Cleyet wrote:

I think energy is quantified as a scalar. As both below agree, light is
also characterized vectorily, etc. therefore, ....

bc, wonders if "anything" is pure energy. Seems analytic: a thing is
energy?

John Denker wrote:

J. Schnick asks: "Is light pure energy?"

On 07/03/2007 07:15 PM, Dan Crowe wrote:


Not in my book. Energy is one property of light. Light also has
momentum, frequency and polarization/helicity.



Agreed.

I might have added that light has observable electromagnetic fields
that other forms of energy might not have. Also note that the
polarization/helicity is also connected to angular momentum,
which is often well worth paying attention to.



The phrase "converted totally to energy" bothers me.



Me too.



I think I would
have said something to the effect that the matter is converted into
light that has the same amount of energy m_o c^2 that the matter had
prior to the conversion. Is light pure energy?



I would have said _rest energy_ in the amount of m c^2.
The electron and positron had mass, and therefore had rest energy,
whereas the photon is massless (and restless).
http://www.av8n.com/physics/mass.htm

I think we can agree that the electron and positron were _matter_,
whereas the photons are non-matter. I don't know a simple word that
means non-matter; lots of people (not just Feynman) say "energy"
when they mean "non-matter" ... but it is definitely an abuse of
the terminology.

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Forum for Physics Educators
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https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l


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