Quote:
Originally Posted by Karnuvap
The real secret to where they are bamboozling us lies in the expression "Group Velocity". This is not a real velocity that should be used in the subsequent equations. It is a mathematical construct to help solve the equations and not anything real. To give you a clue as to why group velocity isn't anything like real velocity - it is perfectly possible to have a group velocity faster than that of the light photons or waves that make it up (which, obviously, travel at the speed of light themselves).
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First, you're exchanging group and phase velocity, the former is that of the wave "packets" (and hence of the particles) and, second, it will be less than
c; in a dispersive medium, due to the separation of the velocities, it will be even a bit less than
c divided by the refractive index.
Of course, I'm not saying that the contraption could work. It's every bit as pointless as hoping to propel a spaceship with a jar of the same shape filled with hot gas.
Quote:
Originally Posted by Karnuvap
I'd love to know what the real answer was.
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The real answer is that you could never get the two beams to completely have exactly destructive interference from thence onward along the direction of propagation without getting any reflection. I'd say that physics lecturer hadn't thought it all the way through.
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Inutil insegnà al mus, si piart timp, in plui si infastidìs la bestie.
Hypography Forum PITA...... er, Administrator.
