Question

Waves are observed passing under a dock. Wave crests are 8.0 meters apart. The time for a complete wave to pass by is 4.0 seconds. The markings on the post submerged in water indicate that the water level fluctuates from a trough at 6.0 meters to a crest at 9.0 meters. What is the period of the wave?

Answer 1

Answer;

The period of the wave is 4 seconds

Explanation;

• The period of a wave or periodic time is the time taken for one complete oscillation to occur. In this case, one complete oscillation occurs when the wave moves from one crest to the next or a trough to the next. This takes 4 seconds. Therefore the period is 4 seconds.
• Frequency on the other hand is the number of oscillations by a wave in one second. Thus, f = 1/T, that is frequency is the reciprocal of periodic time.

Answer 2

Period of wave is time takes wave to pass the fixed point.
you have been said that it's 4s, that's the answer 
T = 4s