The experimental set-up illustrated above consists of a resonance tube filled with water and a vibrating tuning fork placed closed to the open end of the tube.  When the top is opened and water is let out, the air column above the water in the tube increases until the loudest note is heard coming out of the tube.  The frequency of the vibrating tuning fork is therefore equal to the frequency of the vibrating air column.

The experiment is repeated by vibrating four other different tuning forks of different frequencies. The corresponding resonant lengths are measured and recorded.
Fig. 2 (a) and Fig. 2(b) show the vibrating tuning fork with frequencies fi and the corresponding vibrating air columns Li respectively where i = 1, 2, 3, 4, and 5.

1. Measure and record the frequencies fi.
2. Measure and record the corresponding values Li..
3. Evaluate f- -1 in each case.
4. Tabulate your readings.
5. Plot a graph of L on the vertical axis against f- -1 on the horizontal axis. 
6. Determine the slope, s, of the graph.
7. Evaluate V = 4s.
8. State two precautions that are necessary to ensure accurate results when performing 

this experiment.

1. (i)   Define longitudinal wave.

(ii)  The shortest length of an air column in a tube resonating to a note from
tuning fork is 0.17m.  Assuming no end correction, calculate the frequency of the
tuning fork.
[Speed of sound in air = 340 ms-s]
                                   
This question on resonance tube experiment using vibrating tuning fork was not popular among the candidates.  However, the few that attempted it responded well except in few cases were some candidates are unable to correctly evaluate the reciprocal of the frequency f and those who evaluated correctly did not record it to the required number of decimal places.  Precautions were often not stated correctly. 

The (b) part was not well attempted as some candidates could not properly distinguish between longitudinal waves and transverse waves.
In part (a) candidates were required to perform the following tasks to score points:

1. measure and record correctly five raw values of L and f to at least 1 d.p
2. convert and record correctly five values of L and F to at least 3 s.f.
3. evaluate correctly  five values of f-1 to at least 4 d.p  + 1o    
4. record the data in composite table L, f  and f-1.   
5. plot five points correctly using reasonable scales.
6. distinguish between the axes and draw a line of best fit.
7. draw a large right angled triangle on the graph line in order to determine the slope         
8. state any two of the following precautions;                                                              
1. Avoid parallax error in reading the metre rule;
2. repeat readings;
3. note and correct zero error of metre rule.

 
 (b)(i)   A longitudinal wave is one whose particles vibrate in the same direction (parallel) to the direction in which the wave travels.

   (ii)     Ɩ = λ/4
            λ  =      4 Ɩ = 4 x 0.17 = 0.68m.
            f = v/λ
 = 340
    0.68
          = 500 HƷ