Mosby Ch. 3 - Physics Flashcards
what is Avogadro’s number?
6.0028 x 10^23
zXa what does each symbol represent?
Z- the atomic number (number of protons or electrons)
A- the atomic mass (the sum of protons and neutrons)
what is the speed of light equal to?
3x10^8 m/sec
name the photon interaction: when high energy photons interact with the nucleas; this leads to the emission of one or more nucleons or nueutrons; energies greater than 10 MeV have the greatest probability
photodisintegration
name the photon interaction: when the photon bundle passes near an orbiting electron and sets it into motion; no energy is absorbed by the aton, just redirected; this is probable in high atomic nymber materials and low energy beams less than 10 KeV
coherent scatter
name the photon interaction: when a photon ejects one of the orbiting electrons. The entire energy of the photon is first absorbed by the atom and then transferredto the atomic eectron. Thi happens in the innermost shells. The ejected electron is called a photo-electron. When vacancy occurs, another electron drop in to fill the space and energy emitted is in the form of characterisitic x-rays or auger electrons. the higher the energyy, the greater the probability of this type of interaction
photoelectric effect
name the photon interaction: when a photon interacts with an electron as though it were a free electron. This happens in the outer shell. The encountered electron reveives some energy from the phton and is emitted at an angle from the atom. The photon, with reduced energy, is also scattered at an angle. There could be a direct hit where the electron will move out and foward and the photon will travel backward. The higher the energy, the smaller the probability of this time of interaction. This effect is independent of atomic number of the matierial
comptom effect
name the photon interaction: occurs when the photon energy is greater than 1.02 MeV. The photon interacts with the electromagnetic field of the nucleus and gives up all its energy in the process of creating a pair of particles consisting of an electron and positron. THe particles are emitted in the foward direction; porbability of this type of interaction increases with atomic number
pair production
the amount of energy present per unit of time per unit of area perpendiculat to the beam direction
intensity
the energy of the beam expressed in electron voltsor the absorbing potential or penertrating power of the beam expressed in half value layer of material
beam quality
intensity of the beam is reduced by two effects
beam divergence and attenuation
some photons or particles are unaffeted by the attenuator and pass through; the photons or particles passing through are referred to as
transmission
equation for transmission
transmission=final intensity/original intensity
same number of protons but different number of neutrons
isotopes
same bmber of neutrons but different number of protons
isotones