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  • We are going to explain the reflection of electromagnetic waves (is equivalent for acoustic waves)

  • caused by a mismatch on the impedance value of the propagation medium

  • We suppose an incident wave travelling in the +x axis following a sinusoidal form (blue)

  • When the incident wave arrives to the end of the medium, we must calculate the reflection coefficient, which depends on the relationship of the two medium impedances.

  • If this reflection coefficient is equal to -0.35 the reflected wave (red) is going to have an amplitude 0.35 times the amplitude of the incident wave and a phase shift of 180 degrees.

  • The resulting (total, stationary) wave is the sum of the two waves (green)

  • Now we animate the two waves and we see what really happens with a set of different reflection coefficients

  • For a reflection coefficient of -1 all the incident wave is reflected with a phase shift of 180 degrees

  • This causes that the stationary wave takes value from 0 to 2 times the incident wave peak)

  • As we can see the positions of the maximums and minimums (nulls) are fixed

  • For a reflection coefficient of -0.5 half of the incident wave is reflected with a phase shift of 180 degrees

  • Now the interference of the two waves don't cause nulls and maximums with two times the incident wave peak value

  • For a reflection coefficient of 0 the mismatch doesn't exist, so there isn't reflected wave and the incident wave is directly the stationary wave (blue and green waves are overlapping)

  • Of course the maximum value is the same across all the distance

  • For a reflection coefficient of 0.5 half of the incident wave is reflected with no phase shift between them.

  • Is equivalent to the -0.5 case. The unique changes are the positions of maximum and minimum values of the stationary wave.

  • For a reflection coefficient of 1 all the incident wave is reflected with no phase shift between them.

  • Is equivalent to the -1 case. The unique changes are the positions of maximum and minimum values of the stationary wave.

  • Thanks for watching

We are going to explain the reflection of electromagnetic waves (is equivalent for acoustic waves)

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B2 中上級

立つ(据置)波動レッスン(動画あり (Standing (Stationary) Waves Lesson with Animation)

  • 45 0
    Weihao Lu に公開 2021 年 01 月 14 日
動画の中の単語