Question

a sound produced at 13 crest and 15 troughs in 3 seconds when the 2nd crest is produce the first is 2 cm away from the source calculate wavelength frequency and wave speed

Answer 1

if the sound produces 15 crests and 15 troughs in 3 seconds it means that it is producing 15 waves in 3 seconds
it means the sound produces 5 waves in 1 second.
so the frequency of the sound wave is 5Hz

given that λ=2cm   =0.02m
so wavelength =0.02m
wave velocity  v=υλ
                       v=5*0.02
                       v=0.1m/s
  

Answer 2

Answer:

Answer is in the above attachment.