Why is there an antinode at the open end of a tube?

[amk_dbz]

Why do we assume that an antinode is present at open end of a tube?
Can a node be possible at open end?
Thank you in advanced.

 

[tiny-tim]

hi amk_dbz!

how can there be a node at an open end ?

there's a node at a closed end because the air can't move there (in the pipe, air only moves longitudinally, of course)

there can be nodes in the middle of the pipe, but only because of interference from reflection from both ends

at the open end, there's nothing on the "outside" side to reflect from, so no interference and no node!

(and if there's a standing wave, the end must be either a node or an anti-node, so in this case, it's an anti-node)

btw, the anti-node is actually just outside the open end … you need to apply an "end correction"

for details, see my favourite sound site, http://www.phys.unsw.edu.au/jw/flutes.v.clarinets.html#time