The formula is used to measure the speed of ocean waves, like tsunamis, that have very long wavelengths relative to the depth of the water. Tsunamis can have wavelengths greater than 700 kilometers (the average ocean depth is 3-4 kilometers). The formula estimates the tsunami's speed while it is in deeper waters (as it approaches shallower coastal waters, the tsunami slows down, its wavelength shortens, and its height increases).
Head lice and their eggs (nits) soon perish if separated from their human host. Adult head lice can live only a day or so off the human head without blood for feeding. Nymphs (young head lice) can live only for several hours without feeding on a human.
How long do head lice live? The life span of an adult louse on a host ranges up to 30 days. During this time, the female head louse can deposit about 90 eggs. After incubating for seven to 10 days, the nits hatch and, after another 10 days, mature into adult head lice and the cycle begins again.Off the host, adult head lice can live about two to four days at 74 degrees Fahrenheit (F) and one to two days at 86 degrees.Nits will remain alive off the host for up to 10 days; they will not hatch at or below room temperature (68 degrees F).fter incubating for seven to 10 days, the nits hatch and, after another 10 days, mature into adult head lice and the cycle begins again. Off the host, adult head lice can live about two to four days at 74 degrees Fahrenheit (F) and one to two days at 86 degrees.