Which letter from the Greekalphabet is the symbol of the most penetrating type of radiation containing no particles ?
Discovery of the neutron experiments at the time. Alpha radiation can be influenced by an electric field, because it is composed of charged particles. The observed penetrating radiation was not influenced by an electric field, however, so it was thought to be gamma radiation. The radiation was more penetrating than any gamma rays known, and the details of experimental results were difficult to interpret. Two years later Irène Joliot-Curie and Frédéric Joliot in Paris showed that if this unknown radiation fell on paraffin wax, or any other hydrogen-containing compound, it ejected protons of very high energy (5 MeV). This observation was not in itself
Radiation knocking out electrons and ionizing materials, but since most have an electrical charge, they don't have the penetrating power of ionizing radiation. The exception is neutron particles; see below. There are several different kinds of these particles, but the majority are alpha particles, beta particles, neutrons, and protons. Roughly speaking, photons and particles with energies above about 10 electron volts (eV) are ionizing (some authorities use 33 eV, the ionization energy for water). Particle radiation from radioactive material or cosmic rays almost invariably carries enough energy to be ionizing. Most ionizing radiation originates from radioactive materials and space (cosmic rays),