[ 49 ] Earth and Space Science GED ® TEST SCIENCE FLASH REVIEW • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • This diagram illustrates the structure of an ocean wave. Direction of travel Wavelength Wave height Trough Crest Calm sea level A B The period of a wave is the time required for the wave crest at point A to reach point B. The wave period can also be described as the amount of time required for a wave to do which of the following? A. reach the shoreline B. travel one wavelength C. return to calm sea level D. travel from crest to trough