2. Nuclear physics, radioactivity, radiobiophysics.

Electrostatic interaction (Weak interaction)

created between two opposite-sign charges (+, −) and repulsive is created between two identical signs (+,+ or −,−).

It is a long-range, but weak

Coulomb's law

the force between two point charges is directly proportional to the charges and inversely proportional to the square of the distance between them

Nuclear force (strong)

is a force between two or more nucleons. This keeps protons and neutrons together, which are capable of forming nuclei. It is a strong interaction.

 Itis a short-range interaction

Independent of the charge (same magnitude between two protons, two neutrons and a proton and neutron)

 Always attractive interaction

Stability of the Nucleus

>83 protons is unstable

Radioactivity

is the process of decomposition of unstable nuclei. This creates high-energy ionizing radiation.

Ionization

is the process of producing an electrically charged ion from a neutral atom or molecule.

Isotopes

are variants of a particular chemical element which differ in neutron number

Alpha decay

an alpha particle (2 4𝛼2+ or 2 4He) is released from the nucleus. The alpha particle is the nucleus of the most common isotope of helium, the helium-4 isotope, an extremely stable nucleus. The mass of the new nucleus is reduced by 4 and its number atomic number is reduced by two during alpha decay

Beta decay

high-energy and high-speed electrons or positrons ejaculate from the radiating material

Negative beta

occurs when a neutron transforms to a proton, while an electron and an antineutrino are leaving the atom. In this case, the mass number does not change,

the atomic number increases by one: 0 1 𝑛 →1 1𝑝+ + 0 0𝑒− +�

positive beta

a proton transforms into a neutron while a positron and a neutrino are released. The mass number is unchanged

the atomic number reduces by one: 0 1 𝑝+ → 0 1𝑛 + 0 0𝑒+ +�

Gamma decay

After alpha or beta decay the nuclei usually still have excess energy, and the excess energy is radiated in the form of gamma-photons

Half-life

the period during which the number of undecayed nuclei decreases to half of the initial number

Activity

number of nuclei decomposing over time:

becquerel

One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second

Photoelectric-Effect

The gamma-ray photon transfers all its energy to an inner shell electron and it causes the inner shell electron to be ejected.

Compton-Effect

The gamma-photon loses some energy, which is transferred to an outer shell electron, and the outer shell electron is ejected from the atom.

Pair-Production

A photon is converted into an electron-positron pair near a heavy nucleus. The condition for pair production is that the electromagnetic energy must be equal to a specific quantity.