Answer :
start the stopwatch just after a wave reaches the pier.count 10 more wave speak reaches the pier. Stop the stopwatch when the 10th peak reaches the pier.
Period of one wave = P = (Time measured) ⁄ 10
Frequency = f = 1 ⁄ P
Period of one wave = P = (Time measured) ⁄ 10
Frequency = f = 1 ⁄ P