Question

A certain organ pipe, open at both ends, produces a fundamental frequency of 285 Hz in air. Part A If the pipe is filled with helium at the same temperature, what fundamental frequency fHe will it produce? Take the molar mass of air to be 28.8 g/mol and the molar mass of helium to be 4.00 g/mol . Express your answer in hertz. View Available Hint(s)

Answer 1

Answer:

Explanation:

In an open organ pipe in fundamental mode of vibration

wave length of wave λ = 2L

where L  is length of  the pipe

frequency   = velocity of sound / λ

285 = 340 / 2 L

L = 59.65 CM

If the pipe is filled with helium at the same temperature, there will be change in the velocity of sound .So frequency of note produced will be changed .

velocity of sound is inversely proportional to  square root of molar mass of gas

velocity of sound in air / velocity of sound in helium = √4 / 28.8

340 / v =  0. 3725

v   =  912.75  m /s  

frequency

  = velocity of sound / λ

= 912.75 / (2 x . 5965)

= 765 Hz