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When you superpose two 100w coherent laser beams, the resultant
power is indeed 400w This is correct if the two beams are coherent and have the same polarization. Very hard to do at optical frequencies, much easier at lower frequencies. Hi Tor, We've seen the math pencil-whipped both ways now to cover all the available answers. The devil's in the details that are not found in: Itot = I1 + I2 + 2*Sqrt(I1*I2)cos(theta) not to mention the glaring mistakes of the first posting of this formula. So? Superposition works. With a yagi antenna, through superposition you get an EM wave which has larger intensity in certain directions than for a single dipole with the same power. Someone far away can't tell the difference between switching to a yagi and turning on a linear. What the formula doesn't say is that in any real system, the wave must have a finite extent (not be a infinite plane wave). Then there must be destructive interference in some directions. So there isn't a problem with conservation of energy. Tor N4OGW |