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question 3 please! dont copy/paste other answers as I will flag them. EM plane w

ID: 2269211 • Letter: Q

Question

question 3 please! dont copy/paste other answers as I will flag them.

EM plane waves ED 26 3. When the complex exponential is written as etkto), there is a total of four possible combinations of plusses and minuses in the argument. For each combination, determine the direction of wave propagation. Explain based on how position and time must change to keep the argument the same. a. i(+kx + ) i(+kx-or) Based on your answers above, does the direction of wave propagation depend on the sign of kr, the sign of , both, or neither? b. A plane wave is defined by E-E,,ei(x-2y+ore, where is a positive number.

Explanation / Answer

The direction of a plane wave is determined by the sign of 'kx' term (if it's along x-direction) not by the 'wt' term. Hence, in the first two cases, the wave is traveling along the positive x-direction, while in the last two cases, it is along the negative x-direction. Also, it is interesting to note that the energy of the second and third waves are positive while in the case of first and last, it has negative energy.