Experiment: To compare the frequencies of two tuning forks by finding the first and second resonance positions in a resonance tube.
An air column can be driven to resonance using a vibrating tuning fork. Resonance occurs when the length of the air column is equal to an odd multiple of λ/4. If ΔL is the difference in the lengths of air column for successive conditions of resonance, then the wavelength of sound waves is given by
λ = 2 ΔL
If f is the frequency of the sound source, the velocity of sound is
v = fλ
Since the velocity of sound is constant in a given condition, for two tuning forks of frequencies f1, and f2,
f1λ1 = f2λ2
f1/f2 = λ2/λ1
Combining the equation,
f1/f2 = ΔL2/ΔL1
Resonance tube apparatus, tuning forks, rubber mallet or block, meter stick (if measurement scale not attached to the resonance tube)
1. Follow the procedural steps 1 to 8 in this experiment.
2. Repeat the experiment for the second tuning fork.
3. Record the position for the first and second resonance for the two tuning forks in the observation table.
4. For each length of resonating air column, calculate the average of the three readings taken.
5. Calculate the difference (ΔL) between length of resonating air column for the second and the first position for the two tuning forks.
6. Calculate the ratio of ΔL’s for the two tuning forks.