Don't you mean a half cycle (∏ of angle)? It's the 1/2 spin electron that takes 4∏ rotation to return (a weird QM thing I don't fully understand).Mentz114 said:It's eaiser to see that a grav wave takes 2 complete cycles (4∏ of angle) to return to its initial state,...
Q-reeus said:Don't you mean a half cycle (∏ of angle)? It's the 1/2 spin electron that takes 4∏ rotation to return (a weird QM thing I don't fully understand).
I don't know how classical angular momentum is related to spin.
In physics, intensity is a measure of the energy flux, averaged over the period of the wave...To find the intensity, take the energy density (that is, the energy per unit volume) and multiply it by the velocity at which the energy is moving.
Indeed, a beam of light, while traveling approximately in a straight line, can also be rotating (or “spinning”, or “twisting”) around its own axis...Less widely known is the fact that light may also carry angular momentum, which is a property of all objects in rotational motion. For example, a light beam can be rotating around its own axis while it propagates forward. Again, the existence of this angular momentum can be made evident by transferring it to small absorbing or scattering particles, which are thus subject to an optical torque.
...By carrying these away from a source, waves are able to rob that source of its energy, linear or angular momentum. Gravitational waves perform the same function. Thus, for example, a binary system loses angular momentum as the two orbiting objects spiral towards each other—the angular momentum is radiated away by gravitational waves...
There is a little discussed apparent paradox here not at all mentioned in the Wiki references given in #5. A truly plain circularly polarized EM wave carries zero angular momentum density, yet 'in practice' there is indeed a non-zero averaged value as per above - that requires interference fringes for explanation. The freely downloadable article at http://www.opticsinfobase.org/abstract.cfm?id=84895 goes into the details, complete with coloured diagrams. As to any parallels with GW's I would rather not venture an opinion.Bill_K said:...A circularly polarized wave does carry angular momentum. The ratio of the angular momentum density L to the energy density U is (Jackson, problem 6-12) L/U = ± 1/ω. (Compare this to a photon, where L/U = ± 1ħ/ħω.)...
The ratio of the angular momentum density L to the energy density U is (Jackson, problem 6-12) L/U = ± 1/ω. (Compare this to a photon, where L/U = ± 1ħ/ħω.)
I just meant that the classical calculation gives you the same result for L/U that you expect for a photon.[2] What does this mean:
I just meant that the classical calculation gives you the same result for L/U that you expect for a photon.
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