Calculating Wavelength of Sound Using Tuning Fork and Submerged Pipe

[Hellohi]

Homework Statement

A narrow plastic pipe is almost completely submerged in a graduated cylinder fulll of water, and a tuning fork is held over its open end. The pipe is slowly raised from the water. An increase in loudness of the sound is heard when the pipe has been raised 17 cm and again when it has been raised 51 cm.

A) Determine the wavelength of the sound produced by the tuning fork.

B) If the pipe continues to be raised, how far from the top of the pipe will the water level be next increase in loudness is heard?

Homework Equations

T= delta t/N
F= N/delta t
F=1/T

V=F(lamda)
Fbeat=|F2-F1|

The Attempt at a Solution

Hello people, I'm having a problem understanding the section on this and the question I posted above is the very first question. My teacher said I can't use the formula Ln=(2n-1)lamda/4 or Ln= nlamda/2 . Could you please show me how to do this question with the formulas I listed above? Fast help would be appreciated. Thank you very much in advance.

 

[gneill]

I usually find it easier to make a drawing and sketch in the envelope of a 'typical' pressure wave that is resonating inside the enclosure. A simple rule is that pressure minima (where the envelope pinches down to zero width) 'want' to land on a surface, whereas the pressure maxima want to land in free space (want to occupy the full width of the pipe). The pattern is somewhat like stacked figure-eights (or interlaced sine waves).

Take a look http://www.physics1.howard.edu/undergraduate/Labs/GenLab1/10-resonance.pdf" .

Figure 3. is apropos.

 

[Hellohi]

hello thank you for your help.