Light will travel though a vacuum. Because we need somewhere to start. This is called a Hz. Therefore longer wavelength means lower frequencies and vice versa. To me the most interesting characteristic about light is its interaction with matter.
Different interactions are possible.
If , how, and how much interaction there is between light and atoms depends on the energy of light and the kind of atoms or molecules. Let's get a few fundamentals under our belts so we can describe a few different kinds of these interactions. The following two light equations allow you to describe the energy, frequency, and wavelength of a light wave completely. As elsewhere the brackets connote multiplication. For different waves, as wavelength increases frequency decreases and vice versa.