A cylindrical tube, open at both ends, has a fundamental frequency f0 in air.
The tube is dipped vertically into water such that half of its length is inside
water. The fundamental frequency of the air column now is
[RPET 1999; RPMT 1998, 2000; J & K CET 2000;
KCET 2002; BHU 2002; BCECE 2003]
nopen=v2lopen
nclosed=v4lcloes=v4lopen2=v2lopen
(As lclosed=lopen2) , i.e. frequency remains unchanged.