Problem 8.14 in book: The ionosphere, which is the layer of atmosphere located in the region 50 to 500 km above the Earth, has a density of free electrons just like a metal. (a) If the free electron density is 106 electrons per cubic centimeter, determine the plasma frequency of the ionosphere in Hz. (b) A metal is transparent to radiation with frequencies higher than the free-electron plasma frequency (this is usually in the ultraviolet range), and reflecting at lower frequencies. Determine the wavelengths at which the ionosphere becomes transparent, and those at which it becomes reflecting. (c) Is it transparent to at least some radio waves