1) A pipe of length 85 cm is closed from one end. Find the number of possible natural oscillations of air column in the pipe whose frequencies lie below 1250 Hz . The velocity of sound in air is 340 m/s. A) 12 B) 8 C) 6 D) 4 Answer: Option CExplanation:For closed organ pipe = $\frac{(2n+1)v}{4l}$ [n=0,1,2,...] $\frac{(2n+1)v}{4l}<1250$ $(2n+1)<1250\times\frac{4\times0.85}{340}$ $(2n+1)<1.25\Rightarrow 2n<11.50$ n<5.25 n=0,1,2,3,...5 we have 6 possibilities
