Ionizing radiation Flashcards
Matter:
Anything that has mass
and occupies a space
The — is the basic unit of all
matter
atom
Nucleus:
Protons + Neutrons
Atomic number (Z)
(3)
ex
▪ Number of protons
▪ Same as #of electrons in a
neutral atom
▪ Determines the identity of the
atom
▪ Example: Ca has 20 protons
(Atomic number is 20)
Atomic mass (A)
(1)
▪ Number of protons + neutrons
tugesten
184, 74
BINDING ENERGY
• The amount of energy
required to remove an
electron from its shell.
BINDING ENERGY
measured in
Measured in electron Volts
(eV)
Within a given atom, inner
shells electrons are
more
tightly bound (K>L>M, etc)
The electron binding energy is
related to the atomic number.
High Z: more protons → Electrons
are more tightly bound.
Electron = protons →
Neutral atom
Ionization
▪ Process of forming a positive and negative ion by removal of an electronfrom an neutral atom
If a neutral atom loses an electron becomes a — ion and the free electron becomes a — ion.
positive
negative
To ionize an atom, we need sufficient external energy to overcome the
electrostatic forces and free the electron.
Radiation
▪ Is the transmission of energy through space (vacuum) and matter
Radiation
It may occur in two forms:
wave theory or quantum (particles) theory
Wave theory:
explains the propagation of radiation
Quantum theory:
explains the interaction of radiation withmatter.
Waves Theory: Electromag. Radiation
▪ Propagation of radiation in form of waves (no mass) traveling at the
speed of light
Waves Theory: Electromag. Radiation
▪ Why electromagnetic?
Movement of energy through space as a
combination of electric and magnetic fields.
Wavelength:
Distance between two successive crests
Frequency:
Number of wavelength passing a particular point in time
High energy radiation:
High frequency, short wavelength
Low energy radiation:
Low frequency, long wavelength
Non-Ionizing
▪ Does not have sufficient energy to
eject an electron from the shells
Ionizing
▪ Have sufficient energy to eject
an electron from the shells
Quantum theory:
explains the interaction of radiation with matter.
Quantum theory:
▪ Considers radiation as small discrete bundles of energy called —.
photons
▪ Each photon has (3)
energy (eV), mass and travels in straight lines at the speedof light.
particles are — charged (except neutrons and x-rays)
Electrically
▪ Energy: Directly proportional to —, inversely proportional to
—.
frequency
wavelength
High frequency means short wavelength →
High energy
Low frequency means long wavelength →
Low energy
Ionizing rate: Linear energy transfer (LET)
▪ Rate of loss of energy from a particle as it moves through matter
Ionizing rate: Linear energy transfer (LET)
▪ Depends on (3)
velocity, charge and size.
– Lower velocity, higher charge and bigger size →Greater LET
– Higher LET: Less penetration because they lose their energy after short distances
What are X-rays?
▪ They are weightless* packages of pure energy (photons) without an
electrical charge which travel in waves with a specific frequency and
wavelength at the speed of light (3x108 m/sec) and are able to ionize
matter.
Properties of X-rays
(7)
- Invisible, weightless*, no electric charge
- Travels in straight lines.
X-ray beam diverges over distance. - Travel at the speed of light
- Highly penetrating (short wavelengths)
0.01 nm to 0.1 nm - Differentially absorbed by matter
- Can ionize matter
- Produce biological changes
Excitation
(2)
▪ When the transferred energy is not sufficient to overcome binding
energy, e- is NOT ejected
▪ Receiving e- is raised to higher energy level within the orbit.
Instantaneously gives up this excess energy and returns to ground
level
