1. An air column has a length of 0.310 m and is open at both ends. What is the l

Question

1. An air column has a length of 0.310 m and is open at both ends. What is the lowest frequency of a standing wave that can be found in such a column? (Take the air temperature to be 20°C.)

2. An interesting demonstration of standing waves can be done by twirling one end of a flexible, corrugated hose that is open at both ends. The twirling motion causes air to be drawn through the hose, and air rushing over the corrugations creates turbulence in the hose. The turbulence excites waves. It is usually possible to get the three lowest tones from the hose. For a 4.22 m hose, what frequencies will be heard? (Take the air temperature to be 20°C.)

f1

f1

Explanation / Answer

1)

length of the air column. l=0.31 m

speed of the sound, v=332+0.61*T

v=332+0.61*20

v=344.2 m/sec

now,

in case of open pipe,frequency f=v/2l

f=344.2/(2*0.31)

f=555.2 Hz

2)

length of the open pipe, l=4.22 m

speed of the sound, v=344.2 m/sec

f1=v/2*l

f1=344.2/(2*4.22)

f1=40.8 Hz

and

f2=2*f1=81.56 Hz

f3=3*f1=122.34 Hz

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