Answer:
a) The frequency of the waves are = 2 Hz (since you are making two pulses every second)
b)The period of the waves is 0.19 m (as the consecutive crests are separated by 0.19 m)
c) V = L x f
v = 0.19 m x 2 S-1 (Hz is actually per second)
v = 0.38 ms-1
pe nis