Part(a) a good number of the candidates were able to explain interference of waves and applied the knowledge to distinguish between constructive and destructive interference of transverse waves.
Part(b) majority of the candidates that attempted this question performed poorly. Majority of the responding candidates only scored for the formula f = k the substitution and simplification was poorly rendered.
Part(c) was well attempted by majority of the candidates.
The expected answers are:
Interference of waves is the super position (coming together) of two or more progressive waves to form a resultant wave.
Constructive interference Destructive interference
(b) f = KT
f1 = 60 = kT ……………….. (1)
f2 = k T ………………… (2)
Divide equation (2) by equation (1)
= T
T
F2 = X 60
f2 = 90Hz
(c) y = 12.5 Sin ( 420 t - 0.50px)
Comparing the given equation with the standard equation
y = a Sin 2pt - 2
T
(i) W = 2pft [ 1 ] = 420pt [ ½ ]
f = 210Hz [ ½ ]
(ii) 2p
l = 0.50px
l =
= 4m
(iii) V = f
= 210 x 4
= 840 ms-1
