• jsomers
I'm not sure what you're asking. The Einstein field equations couple c and the stress-energy tensor: R_{\mu \nu} - {1 \over 2}g_{\mu \nu}\,R + g_{\mu \nu} \Lambda = {8 \pi G \over c^4} T_{\mu \nu}f

#### jsomers

Hi People

I am brand new to these forums and brand new to phyics (wells its been about 4 years so its safe to say I have pretty much forgotten everything but the basics)

Anyhow I am just beginning my PhD in Genetics where I will be using Förster resonance energy transfer to investigate the assembly of particular proteins. In my quest to understand the physics behind this phenomenon I came across this diagram:

http://www.olympusmicro.com/primer/techniques/fluorescence/fret/images/fretintrofigure3.jpg

What I don't really understand from it is what is the difference between radiant energy and non-radiant energy.

Forgive me if this is very basic but google has been little help so i thought id ask here.

Jason

What I don't really understand from it is what is the difference between radiant energy and non-radiant energy.

Energy transferred by resonance, or by kinetic energy going from one atom to another, is non-radiant energy transfer.

Cheers -- sylas

Wow that was simple, thanks for the speedy reply!

The transfer of energy does not invovle kinetic mechanisms, for FRET.

FRET is a non-radiant form of energy transfer by a dipole-dipole interaction. It's called non-radiant because there is no photon involved in the transfer of energy, only the evanescent (non-propagating) component of the electromagnetic field. This is why FRET experiments are sensitive to both separation distance and relative orientation of the two dipoles.

The transfer of energy does not invovle kinetic mechanisms, for FRET.

FRET is a non-radiant form of energy transfer by a dipole-dipole interaction. It's called non-radiant because there is no photon involved in the transfer of energy, only the evanescent (non-propagating) component of the electromagnetic field. This is why FRET experiments are sensitive to both separation distance and relative orientation of the two dipoles.

Ah. Thanks... and sorry if I lead jsomers up the garden path!

Yeah, I have heard there is a fair bit of information you can draw from the occurrence of FRET that's why I am sure i'll be inhabiting these forums for the next three to four years to try to gain a greater understanding of my experiments!

No stress sylas, you still provided me the answer to my question about radiant and non radiant. For a genetics crowd it is more then enough info.

On a some what similar note: The Einstein field equations couple c and the stress-energy tensor:

$$R_{\mu \nu} - {1 \over 2}g_{\mu \nu}\,R + g_{\mu \nu} \Lambda = {8 \pi G \over c^4} T_{\mu \nu}$$

Does this not imply that gravity is a radiating field of a photonic nature? Otherwise why would c be a component?

Frank

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