A one metre long (both ends open) organ pipe is kept in a gas that has double the density of air at STP. Assuming the speed of sound in air at STP is 300 m/s, the frequency difference between the fundamental and second harmonic of this pipe is _______Hz

Speed of sound in a gas =V=Bρ​∴VpipeVair=B2ρBρ=12⇒Vpipe=Vair2=3002m/s​Now, frequency in open organ pipe =fn=n+1Vpipe2lFundamental frequency =f0=Vpipe2l​Second Harmony = f1=2Vpipe2lThus, frequency difference =f1−f0=Vpipe2l=30022=106.38Hz  If2=1.41or f1−f0=106.08Hz If2=1.414