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# there are alternatives the two sources could be out

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Unformatted text preview: bruary 24, 2013 Maxima and Minima Algebra Assume that the two sources are in phase. For maxima, we want constructive interference: r2 - r1 = mλ, with m = 0, ±1, ±2, ... For minima, we want destructive interference: r2 - r1 = (m+½)λ, with m = 0, ±1, ±2, ... There are alternatives - the two sources could be out of phase. In this case we obtain minima where there were maxima, and vice verse. More generally, there could be any phase difference between the two sources. Sunday, February 24, 2013 Radio Stations Consider a radio or TV station w ith a single vertical dipole antenna. It will broadcast its signal equally in all directions along the surface. But if we add a second antenna, The interference pattern results in more energy going o ut in some directions - so the signal can be received further away - and less going out in other directions. Sunday, February 24, 2013 In the conﬁguration shown, interference reduces the energy going out in some sideways directions. If we changed the antennas to be out of phase, interference would reduce the energy going to the left and right. iClicker: You are going to use two antennas to broadcast radio mainly east/west from the center of Long Island. The antennas have to be east/west of each other. Should they be in phase or out of phase?How many wave lengths apart should they be? Choose the best answer a) b) c) d) e) 0λ in phase. 0λ o ut of phase. ½λ o ut of phase. ½λ in phase. 1λ, phase does not matter. Sunday, February 24, 2013...
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