Which one of the following statements concerning the wavelength of an electromagnetic wave in a vacuum is true? A) The wavelength is independent of the speed of the wave for a fixed frequency. B) The wavelength is inversely proportional to the speed of the wave. C) The wavelength is the same for all types of electromagnetic waves. D) The wavelength is directly proportional to the frequency of the wave. E) The wavelength is inversely proportional to the frequency of the wave.