Phase of reflected and transmitted waves

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    Phase Waves
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SUMMARY

The discussion centers on the treatment of reflected and transmitted electromagnetic (EM) waves as presented in Griffiths' textbook. The key point is that Griffiths simplifies the calculation of real amplitudes by disregarding the exponential part of the complex amplitudes, effectively assuming that the phase of the reflected and transmitted waves aligns with that of the incident wave, except for a 180-degree phase shift in the reflected wave when transitioning from a medium of higher to lower impedance. This assumption is based on established principles of wave behavior at interfaces, which are foundational in electromagnetic theory.

PREREQUISITES
  • Understanding of electromagnetic wave theory
  • Familiarity with complex amplitudes in wave physics
  • Knowledge of wave behavior at material interfaces
  • Basic principles of phase shifts in wave reflection and transmission
NEXT STEPS
  • Study the derivation of the Fresnel equations for reflection and transmission
  • Learn about phase shifts in wave mechanics, particularly at boundaries
  • Explore Griffiths' "Introduction to Electrodynamics" for detailed examples
  • Investigate the implications of impedance mismatches in wave propagation
USEFUL FOR

Students of physics, particularly those studying electromagnetism, educators teaching wave behavior, and researchers focusing on wave interactions at material interfaces.

carllacan
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I'm reading the EM waves chapter on Griffiths, and, after getting the complex amplitudes of the reflected and transmitted waves he obtains the real amplitudes by (apparently) just "disregarding" the exponential part, which is equivalent to assuming that the phase of both waves is equal to the phase of the incident wave (except for the minus charge in the reflected wave if v2 < v1). Why does he assume this?
 
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Can you provide the equation related to what you describe there?
Besides, the presence of minus implies that the phase has been flipped 180 degree, that is the phase is not omitted.
 
Not familiar with the Griffiths book, but what you are describing seems like the most elementary thing about how waves behave at an interface. I'd say it's assumed as a hypothesis, because he knows it turns out to be true. What is the author coming to at the end of the demonstration?
 

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