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.
Head lice only survive on human blood. Without a human hosts, most lice will only live for a maximum of 48 hours. This is why sealing clothes and toys after infection in a plastic bag is a great way to get rid of lice. Lice on a human host can survive two or three weeks. However, living lice lay eggs.ithout a human hosts, most lice will only live for a maximum of 48 hours. This is why sealing clothes and toys after infection in a plastic bag is a great way to get rid of lice. Lice on a human host can survive two or three weeks.