Standing waves are causing great confusion for me. I have read many answers on stackexchange. However, I still don't understand standing waves within closed and open tubes.
Problem 1. I struggle to understand why there must be an antinode on the open end. However, I understand why there must be a node at the closed end. My intuition here, is that the sound wave reflects at this point, and overlaps with the incoming sound wave causing destructive interference. Hence a node. Now the antinode at the open end is not so trivial. I understand that there is nothing blocking it so it can have maximum displacement. However, why does it have to have this maximum displacement. Could a node just as well form at the open end? When discussing with my teacher, he said that it is possible to have a node at the open end, but you wouldn't hear anything. Is this correct? Could it be that you can have a node, but then it no longer exists as a harmonic?
Problem 2. All diagrams I have seen, draw the antinodes tocuhing the walls of the pipe. However, I struggle to understand why this must be the case. Could I not have a small standing wave that doesn't touch the walls of the pipe. That is the yellow lines amplitude is shrunken such that they don't touch the walls of the pipe. What is limiting this?
For example this. Here the lines do not touch the tube.
Edit: Consider sending a wave with a wrong frequency such that there is no formation of a standing wave. Can we have a node at the open end then?
A comment on the linked post states there can either be an antinode or a node at the open end but you wouldn't hear a sound if they were nodes (or at least it wouldn't be very harmonic). Is this correct? This aligns with what my teacher has said.
I am trying to understand which statement is correct.
That is there can be either an antinode or a node at the open end, but a node results in it not being a harmonic.
That it must always be an antinode. If this is true, please explain why this is the case.
Farcher has explained my latter problem superbly. However, I still have confusion about problem 1. I understand that an antinode can form on the open end as it has no restrictions. However I do not understand why there must be an antinode. Shouldn't no restrictions correlate to either being able to exist at the open end?