Given, v=320ms−1,l=1m For an organ pipe whose one end is closed, only odd harmonics containing odd multiples of fundamental frequency are present. Resonate frequency of first mode, n1=
v
4l
Second mode, n2=3n1 Third mode, n3=5n1 Fourth mode, n4=7n1 Fifth mode, n5=9n1 So, n1=
320
4
=80Hz n2=3×80=240Hz n3=5×80=400Hz n4=7×80=560Hz n5=9×80=720Hz So according result, option (b) as multiple of cannot a resonating frequency of the pipe.