Phase change of reflected wave

what do we mean when we say that light wave suffers a phase change of $$\pi$$ when it gets reflected and why does that happen

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Meir Achuz
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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 $${\vec E}_R=-{\vec E}_I$$.
In complex notation, -E=exp(i pi) E.

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G01
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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 occuring 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 [Broken]

-al

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thank u

how do I calculate amplitude and phase for reflected wave? Is the change in phase occurs in all objects

ehild
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