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.
The female louse attaches her eggs (nits) to the base of the hair near the scalp, and the nits hatch 7â10 days later. While the adult louse cannot survive for more than 2 days off the human head, a nit can stay alive for up to 10 days off the body (for example, on clothes, hairbrushes, or carpets).n order to make a diagnosis of head lice, the doctor must see a louse or a nit on the scalp. Occasionally, what is called a Wood's lamp is used to look for lice and nits.