Subatomic particles like protons, neutrons, or electrons can only come from collisions of rays that vibrate very rapidly, because each particle requires a large amount of energy to make it. By the mid-20th century there were accelerators powerful enough to produce pairs of particles from pure energy. The minimum energy for pair production is that required to produce an electron and a positron. The energy a ray can provide is directly proportional to its vibration rate, and inversely proportional to its wavelength. Let’s work with the wavelength, because it is the easier to visualize.