Radiological Science Course PDF

All the matter in the Universe is constructed from 92 elements, either in isolation or in combinations called compounds. An atom is the smallest part of an element that can exist and yet still retain its chemical identity. The nucleus is composed of:  Protons – carry a positive...

All the matter in the Universe is constructed from 92 elements, either in isolation or in combinations called compounds. An atom is the smallest part of an element that can exist and yet still retain its chemical identity. The nucleus is composed of:  Protons – carry a positive charge  Neutrons – uncharged Atomic Number, is the number of protons in the nucleus. The electrons are very light negatively charged particles, which roam around outside the nucleus. They are held in place by electrostatic attraction to the positive nucleus and tend to exist in layers, called “shells”, which surround the nucleus at different distances.  When an electron passes close to a nucleus the strong attractive force (opposite charges attract) causes it to be decelerated rapidly and deflected violently from its original path. As a result, the electron suffers a sudden loss of kinetic energy (ie it slows down) and emits an x-ray photon. The energy of the emitted x-ray depends on the strength of the electron-nucleus interaction and is equal to the kinetic energy lost by the electron, which can be any amount from virtually zero right up to its entire kinetic energy (ie the electron is brought to a complete stop). X-rays produced in this way are known as “bremsstrahlung” x-rays (German for "braking radiation") This creates what is known as the continuous spectrum  13cm² 39cm² 7 cm diameter round cone vs size 2 receptor/film