Alternative A
Question 2A
The diagram above illustrates an experimental set-up in which a burette is used as a resonance tube. The burette is filled with water. A vibrating tuning fork of frequency f is placed close to the open end of burette. The air column is gradually increased until the first position of the resonance is obtained, the resonating length of the air column is measured and recorded. The procedure is repeated using four more turning forks of different frequencies.
Fig. 2(a) and Fig. 2(b) illustrate the frequencies Fi and the corresponding resonating lengths li respecting, where i = 1,2,3,4, and 5.
(i) Measure and record Fi.
(ii) Measure and record the corresponding li.
(iii) Use the given scales to convert Fi and li to the real values fi and Li respectively.
(iv) In each case, evaluate f-1
(v) Evaluate P = 4L in each case.
(vi) Tabulate the readings.
(vii) Plot a graph with P on the vertical axis and f-1 on the horizontal axis.
(viii) Determine the slope, s, of the graph.
(xi) Use your graph to determine the frequency f for which the length of the resonating column L = 20 cm
(x) State two precautions necessary if you were to perform this experiment.
Question 2B
(i) Define resonance.
(ii) The velocity of sound in air at 28°C is 340 ms-1. Calculate the increase in velocity of sound as temperature increases to 32°C.
The expected response:
- Five values of Fcorrectly measured and recorded to at least 1 d.p. and within
tolerance of ± 0.1cm.
- Five values of lcorrectly measured and recorded to at least 1 d.p and within
tolerance of ± 0.1cm.
- Five values of fcorrectly converted in Hz.
- Five values of Lcorrectly converted.
- Five values of f-1correctly evaluated to at least 2s.f
- Five values P = 4L correctly evaluated.
- Composite table showing at least F, l, f, L,f-1and P.
- Plot a graph of reasonable scales
- Draw line of best fit
- Determine the slope
- State any two of the following precautions
e.g
- Avoided/Avoid tuning fork touching the resonance tube
- Avoided/Avoid parallax error on metre rule
- Ensured/Ensure that water does not leak from the tube
- Noted/Note zero error on metre rule
- Repeated/Repeat reading stated
- Ensured/ensure readings are taken at the lower meniscus.
(b) (i) Definition of resonance
Resonance is a phenomenon which occurs when a body is set into vibration at its own natural frequency as a result of impulse it receives from nearby body vibrating at the same frequency. [2 marks or zero]
(ii) 