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 amplitude of the wave?

The amplitude of a wave can be obtained by measuring the distance from the resting position of the wave to its crest. The resting position is half of the distance from the crest to the trough. Given that the distance between the crest and the trough is 3 meters, the amplitude should be half of that, which is 1.5 meters.