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 mite typically is about 95% of the population. They are generally opaque/whitish but will be darker after a blood meal. Although parasitic bird mites need a host mammal to survive and reproduce, research has shown they can survive for extended periods without a host. One Swedish study reported D. Gallinae can live nine months without a host. Several other studies confirm that they live at least eight months without feeding.