# Wave reflection

Please look at the two sources that describe wave reflection.

Hyperphysics states that when a wave meets a rigid surface, it changes phase by 180 deg, such that an upright wave will reflect upright, as to produce a standing wave with the right conditions.
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/standw.html#c1

I've come across many other sources like the following that show a wave hitting a rigid surface resulting in the opposite effect as above.
http://www.acoustics.salford.ac.uk/feschools/waves/string.htm

Are these two different situations? My texts books seems to support both, but they seem to be at odds with each other.

Help

Well I think I understand the problem... please comment

I think the hyper physics site is very misleading.

The reflected wave from an Upright wave becomes flipped (vertically), however by the time it fully emerges from the rigid boundary time has passed and it adds constructively with the next incoming wave.

I don't think the hyperphysics site explains the dynamics correctly.

Help anyone?

I guess my issue is I believe that when a wave hits a rigid material it will "invert" itself, however I don't consider this a 180 phase change.

Look at the following applet on phase and imagine the relfected inverted wave, the phase woudn't change at all.

http://www.indiana.edu/~emusic/acoustics/phase.htm

However if the wave was upright there would be a 180 phase change.

http://www.walter-fendt.de/ph14e/stwaverefl.htm