A tuning fork with a frequency of is held at the open end of a tube filled with water. As the water level is lowered, what are the first and second lengths at which the air column resonates? Use 340m/s for the speed of the sound in air.

First length: ? [m]
Second length: ? [m]

Question

A tuning fork with a frequency of is held at the open end of a tube filled with water. As the water level is lowered, what are the first and second lengths at which the air column resonates? Use 340m/s for the speed of the sound in air.
 
First length: ? [m]
Second length: ? [m]

jamesj · Answer

The pipe you have is half-open, half-closed.  The closed end is the surface of the water.  This must be a node.  The open end must be an anti-node.  

Have a look at this diagram.


 Now, for any wave of frequency f and wavelength L, then the speed of the wave, v, is related to f and L by

v = fL

Here, you have v and f.  So find L.

anonymous · Answer

i did that and it said that it was wrong. i got 0.7727 and the other is 0.386