Phase change of reflected wave

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Discussion Overview

The discussion centers around the phase change of light waves upon reflection, particularly focusing on the conditions under which a phase change of \(\pi\) occurs and the implications of this phenomenon in different media.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants explain that a phase change of \(\pi\) indicates that the reflected wave is inverted, with crests becoming troughs upon reflection, particularly at a conductor where the electric field must be zero.
  • Others argue that the phase change does not occur when the reflecting medium is allowed to vibrate, such as in the case of water reflecting off a wall, suggesting that the fixed condition is necessary for the phase change to occur.
  • One participant inquires about the calculation of amplitude and phase for reflected waves and questions whether the phase change occurs in all objects.
  • Another participant references the Fresnel equations for further understanding of light waves and their reflection properties.

Areas of Agreement / Disagreement

Participants express differing views on the conditions under which a phase change occurs, indicating that there is no consensus on whether the phase change of \(\pi\) applies universally to all reflective scenarios.

Contextual Notes

The discussion highlights the dependence on specific conditions, such as whether the reflecting medium is fixed or allowed to vibrate, which may influence the occurrence of phase changes.

pardesi
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what do we mean when we say that light wave suffers a phase change of [tex]\pi[/tex] when it gets reflected and why does that happen
 
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If it is reflected by a conductor (to make it easy), the E field must be zero at the conductor.
Thus mean that the reflected E field must be equall and opposite to the incident E field.
That is [tex]{\vec E}_R=-{\vec E}_I[/tex].
In complex notation, -E=exp(i pi) E.
 
Last edited:
A phase change of Pi means, in essence, that the wave is flipped upside down after it is reflected. That is, if you have a crest of a wave reflecting off of a boundary, after the reflection, that crest will become a trough. This is due to the electromagnetic boundary conditions at the surface of reflection as Meir Achuz pointed out.
 
pi phase change is not occurring when vibrating media at the reflection point is allowed to vibrate (water bouncing off the wall) but only when it is fixed (attached string)

see visualization: http://www.kettering.edu/~drussell/Demos/reflect/reflect.html

-al
 
Last edited by a moderator:
thank u
 
how do I calculate amplitude and phase for reflected wave? Is the change in phase occurs in all objects
 

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