A problem about standing waves

[VictoriaWoo]

Homework Statement

Why it is the antinode at the open end?

Homework Equations

The Attempt at a Solution

 

[PeterO]

Homework Statement

Why it is the antinode at the open end?

Homework Equations

The Attempt at a Solution

For the standing wave in an organ pipe, displacement nodes correspond with pressure anti-nodes, and displacemment antinodes correspond with pressure nodes.

If you have an antinode at an open end, you must be referring to a displacement antinode [because that is what you get there].

That means a pressure node.

Pressure wise - at an open end, there is no reason for the gas to build up pressure, as it is unconfined.
Displacement wise: being an open end, the gas particles can move in and out at will, so maximum movement is possible → an antinode.

This applet should clarify:
Read carefully, notice which way the particles move and when the particles are crowded together or not.

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