1. Two sunbathers, Anna and Mariah, were sitting on a raft. Anna noted that the raft bobbed up and down with a period of 5.0 s. Mariah noted that a crest took 5.0 s to cover the 15 m to shore. a) What is the speed and frequency of the waves? b) How far apart were the crests? 2. Two students, one on each end, use a skipping rope to produce a standing wave pattern having. The distance from the first to the third node is 6.0 m. a) Draw a diagram of the standing wave pattern produced by waves. b) If the waves are generated at 1.5 Hz, what must be their speed? 3. A submarine sends out a sonar wave that has a frequency of 545 Hz. If the wavelength of the sound is 2.60 m, how long does it take for the echo to return when the sound is reflected from another submarine that is 5.50 km away