A sound wave may be considered either as a displacement wave or as a pressure wave . When reflection takes place from as a rigid wall , what phase change do you except in its displacement representation and in its pressure representation?

Explanation

When reflection takes place from the boundary of two media , the ratio of the amplitudes of the reflected wave and the incident wave is given by
` (a_(r))/( a_(i)) = (c_(1) - c_(2))/( c_(1) + c_(2))`
When there is a rigid wall , `c_(2)` is infinite . Therefore ,
`(a_(r))/( a_(i)) = -1`
or ` a_(r) = - a_(i)`
Thus , the negative sign means that there is a phase change of `pi` in the displacement wave , but there is no change in the amplitude of the wave.
Since a compression is returned as a compression and a rarefraction as a rarefaction from a rigid wall , there is no phase change in the pressure wave.