Answer:
773.25 Hz
Explanation:
Concept : 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
Given values: fundamental frequency = 288 Hz
fluid is air. velocity of sound = 340 m/s
⇒ 288 = 340/2L
⇒L = 59.02 cm
The point to be noted is if the pipe is filled with helium initially at the same temperature, there would be change in the sound velocity .Then, frequency of note produced will also be changed .
We know that velocity of sound is inversely proportional to square root of molar mass of gas
velocity of sound in air / velocity of sound in helium = Square root of (Molar mass of Helium/ molar mass of air)
Now, frequency = velocity of sound / λ
= 912.75 / (2 x 0.5902)
= 773.25 Hz