This question on waves attracted lots of candidates. The performance was fairly satisfactory. Parts (a) and (b) were found tractable by many candidates. However, some candidates lost marks in the definition of frequency and speed because they used per unit time instead of per unit second.
The numerical problem in part © was poorly handled by many candidates. Candidates have not learnt the skill of comparing corresponding terms as a method of solving problems on general wave equation.
The expected answers include:
(i)
Wavelength of a wave is the distance traveled by the wave in one complete
cycle/oscillation of its motion
OR
Distance between two successive troughs/crests.
OR
The distance between two adjacent/successive points of the wave that is in phase /at the same stage of their (harmonic) motion.
(ii)
Frequency of a wave is the number of complete cycles/oscillations made by the wave in one second/per second
(iii) Speed of a wave is the distance traveled by the wave in one second/per second.
(b) (i) Speed = frequency x wavelength
OR
v = ƒ Π
(ii) A stationary wave is produced when two waves of equal amplitudes and frequencies/wavelength which are traveling in opposite direction are superimposed in a medium
(c) (i) Π = 2π
k
= 2 x 22
7
20
= 0.314m
(ii) v = ω
k
= 6.6 x 103
20
= 330ms-1
(iii) T = 2π
ω
= 2 x 22
7
6.6 x 103
= 9.52 x 10s-1
(iv) vmax = a ω
= 1.0 x 10-7 x 6. 6 x 103
= 6. 6 x 10-4 ms-1
