Wavelength is one of the qualities of an electromagnetic wave that helps identify it as what it is. The wavelength helps determine the frequency, which is how many wavelenths pass within one second, using the unit of Hertz. Wavelength does not change for a specific frequency, so it is used to identify the various waves represented on the electromagnetic spectrum. Starting with radio waves, these are at the low end of the spectrum, with the longest wavelengths, with the lowest energy. Next is microwaves, followed by infrared waves. Each successive wavelength is progressively shorter, with more energy. Visible light is next, followed by ultraviolet radiation. Ultraviolet wavelengths are the ones that can give us sunburn and skin cancer. The higheset energy wavelengths are x-rays and gamma rays. These have the shortest wavelengths and pack the most energy.