Given : Frequency of tuning fork, n=264 Hz Length of column L= ? For closed organ pipe n=4lv⇒l=4nv=4×264330=0.3125 or, l=0.3125×100=31.25 cm In case of closed organ pipe only odd harmonics are possible. Therefore value of l will be (2n−1)l Hence option (b) i.e. 3×31.25=93.75 cm is correct.