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.
Life Without a Host. Lice securely adhere their eggs, or nits, to hair shafts on their host. However, once hatched, nymphal and adult lice sometimes fall off their host or get knocked off by the host's scratching.Lice don't quickly die without a host, though, and generally survive for three to seven days on their own.The species, age, environmental factors, when they last fed and other specifics can affect exactly how long a louse is able to live off of a host.ice securely adhere their eggs, or nits, to hair shafts on their host. However, once hatched, nymphal and adult lice sometimes fall off their host or get knocked off by the host's scratching.