In order from shortest to longest frequency, the electromagnetic waves can be ranked :
1. X-rays
2. Ultraviolet
3. Infrared
4. Microwave
X-rays has the shortest frequency which ranges between 30 petahertz to 30 exahertz. X-rays have the smallest wavelengths at 0.01-10 nanometers. Its energy ranges between 100eV to 100keV.