Page 49 - Q & A STPM 2022 Physics

Physics Semester 3 STPM Chapter 21 Sound Waves

(i) In Figure (a), 7.2 + c = 1 λ (1)
4
In Figure (b), 20.2 + c = 3 λ (2)
4
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1
(2) – (1): λ = 13.0 cm
2
λ = 26.0 cm
v
Frequency of tuning fork, f =
λ
= 330 Hz
0.26
= 1270 Hz
(ii) From equation (1),
1
End correction, c = (7.2 – λ) cm
4
1


= 7.2 – (26.0) cm
4
= 0.70 cm
(b) With the frequency oscillation set at a known frequency f, the first
resonance length l of the air column in the burette is measured. The
procedure is repeated for different values of f, and the corresponding
value of l obtained.
1
For the first resonance, l + c = λ = v
4 4f
A graph of l against 1/f is plotted (see figure below).

I (m)

Gradient = v/4

0 1/f (s)

Gradient of graph = v/4
Speed of sound, v = 4(gradient of graph) Semester

3

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021 STPM Q&A Physics T3.indd 409 17/02/2022 10:24 AM