The interaction of heavy charged particles with matter (p.82)

1. Alpha particle is the helium nucleus containing two neutrons and two protons.So we can say that helium nucleus has double charge.While passing through matter, protons and neutrons leave the nucleus at a very high speed knocking out electrons from their shells.Medium atoms become positively charged, and positive ions are formed.Ionizing and penetrating properties of alpha particles are determined by their mass which is very large.Alpha particles are heavily ionizing.A great amount of energy is necessary for the ion production.Initial energy of the particles is lost quickly.The interaction between the alpha radiation and the absorber is that of energy loss.

The interaction of light charged particles with matter (p.87)

1. Beta-radiation is the flow of electrons and positrons. These two particles possess the same mass and charge and have a different half-life.The interaction of β-radiation with matter results in two kinds of energy losses - ionization losses and radiation ones. Ionization losses arise during ionization of the absorber atoms or medium atoms. β -particles have the charge and mass less than those of alpha particles. That is why β -particles possess less ionization but their penetration is greater. β -particles change their direction and velocity.The energy decrease is connected with the emission of brake radiation. Brake radiation is electromagnetic.it is of the same nature as х- and y-radiation.

Gamma Radiation (p.93)

3. The scientists consider gamma rays and X-rays as photon radiation.The origin of these radiations is different but their nature is the same.They are electromagnetic radiation or waves or they are the flow of photons {quanta).Photon radiation has double nature.In some cases this radiation manifests its wave properties (reflection, refraction).in the other cases it manifests properties of the particle (photoeffect, nuclear reactions).Photon radiation has three reactions - photoeffect, Compton-effect, formation of the electron-positron pair.Photoeffect is an interaction between the photon radiation and the absorber.Elastic collision of photon radiation with electrons is called Compton effect.. If the absorbing medium contains light or heavy atoms we observe Compton effect.

Mechanism of Radiation Damage (p.98)

1. Any material undergoes some damage or change on irradiation.In elements the only effect is a change of the crystal structure.Living organisms undergo chemical change.Ionizing radiations passing through living matter produce changes in the heredity of the cell.Mechanism of radiation damage falls into two main groups - direct action and indirect one.Direct action is the breaking of some part of the cell structure by the bombarding particles or photons.In indirect action very active groups of atoms called free radicals are formed.Thus the mechanism of the radiation damage has the following steps:radiation energy absorptionfree radicals formationthe breaking of biochemical reactionthe breaking of physiological reaction