Question

1.A wave has a period of 20 seconds. What is the frequency?

Answer 1

1).  Frequency = (1/period) = 1/(20sec)  =  (1/20) per sec  .

2).  Frequency= (3 waves) / (4 sec) = (3/4) (per sec)
       Period  =  (1/freq)  =  1/(3/4 per sec) = (4/3) sec

3). Speed= (freq) x (wavelength)  (2 per sec) x (5 m)  =  (2 x 5) ( m per sec)
     Speed doesn't depend on amplitude.