MT1 - Nature of Radiation - 2 Qs Flashcards
What is radiation?
The production and emission of energy through space or a material medium
What are the 2 types of radiation?
- Particulate (Corpuscular) Radiation
2. Electromagnetic (non-particulate) Radiation
What kinds of particles are involved in particulate radiation?
- Protons
- Neutrons
- Electrons
- Alpha particles
- Beta particles
What types of energy are involved in elecromagnetic (EM) radiation?
- Radi
- TV
- Radar
- Infrared
- Visible Light
- UV
- Gamma rays
- X-RAYS*
How are EM waves grouped/categorized?
According to wavelength in the EM spectrum
At what speed to EM waves travel in air?
At the speed of light
What is another term for electromagnetic waves?
Electromagnetic Radiation
What is the mass and charge of electromagnetic Radiation?
EM waves have no mass and no charge
How does wavelength correlate to frequency and energy?
Wavelength is inversely related to frequency and energy, therefore a shorter wavelength actually will have higher energy adn higher frequency (and vice versa)
How are x-rays defined?
X-rays are EM radiation with wavelengths shorter than UV but longer than gamma radiation
How are x-rays packaged?
As photons, packets, or weightless bundles
Are the energies and wavelengths of x-rays variable or constant?
X-rays have variable wavelengths and energies
Describe the effect of x-rays on biological molecules
X-rays cause ionization in biological molecules when they interact with the patient’s body.
How are x-rays produced?
Highly accelerated electrons are suddenly brought to a stop by hitting a stationary object, thus causing a fraction of the kinetic energy possessed by the high speed electron to be converted to x-rays.
Who was the 1st person to describe the structure of an atom?
Neils Bohr
What are the 4 parts of an atom?
- Nucleus
- Electrons
- Protons
- Neutrons
What part of the atom makes up over 99% of the mass?
Nucleus
What determines the identity of an element?
The number of protons (Z number)
What is Z number?
Z number is the atomic number, equivalent to the number of protons, which determines the identity of an element
How do Z number and the number of electrons in a neutral atom relate?
Z number will be the same as the number of electrons in a neutral atom
What is the A number?
A number is the atomic mass which is equal to the number of protons plus the number of neutrons
What is the symbol designation for an element’s Z and A numbers?
Z number is written as subscript and A number is written as superscript
How is the charge of an electron related to the charge of a proton?
Electrons have a negative charge equal in magnitude to the positive charge of a proton
How are orbital electrons arranged in the atom?
Electrons are arranged in definitive energy levels (shells or orbits) outside the nucleus at varying distances
How are electrons kept in their orbits?
By electrostatic attraction and centripetal force
How are orbits designated?
Orbits are lettered K, L, M, N, O, P and Q from innermost to outermost
What is the maximum number of orbits in a given atom?
7 orbits
Are orbits limited in the number of electrons they can hold?
Yes. There is a maximum number of orbits that each designated orbit can hold. K orbit can only hold 2 electrons, while Q, the outermost shell, can hold 98 electrons
Define binding energy
Binding energy is the attractive force that keeps electrons in their orbit
How are binding energy and the distance b/t the nucleus and an electron related?
Binding energy is inversely proportional to the square of the distance b/t the nucleus and the electron
Which electrons are most vs least tightly bound to the nucleus?
K shell electrons are most tightly bound while outermost electrons in the Q shell are least tightly bound
How is EM radiation created?
While moving an electron from an outer orbit to the one closer to the nucleus, energy is lost in the form of electromagnetic radiation
How can an electron be removed from its orbit?
To remove an electron from its orbit, an energy greater than the binding energy must be supplied
What electron shells are involved in x-ray production?
Electrons in K, L, and M shells
How are Z number and binding energy related?
The higher the Z number, the higher the binding energy for any particular shell
In particulate radiation, energy is transferred via _____
High velocity subatomic particle
What kind of energy is associated with particulate radiation?
Kinetic energy (KE) is associated with particulate radiation
How does KE relate to mass and velocity?
KE=1/2mV^2, therefore KE is DIRECTLY related to both mass and velocity
How is energy usually supplied when using particulate radiation?
Via electricity
What is the most common clinical application for particulate radiology?
Radiation therapy
What is linear energy transfer (LET)?
The rate of loss of energy of a particle as it moves along its path in an absorber
How is the mass and charge of a particle related to LET?
DIRECTLY related. The higher the mass and charge of a particle, the higher the RATE of TRANSFER of energy to the absorber
How is the velocity of a particle related to LET?
INVERSELY related. The lower the rate of velocity of a particle, the higher the rate of transfer for energy to an absorber
How is chemical composition (Z number), thickness, and density of the ABSORBER related to LET?
DIRECTLY related. Higher Z#, thicker and denser the absorber, the sooner the particle loses energy and is unable to travel.
What travels with the least amount of LET, alpha, beta, or x-ray particles?
X-rays have the least rate of LET and therefore travel furthest and weigh the least. The travel thru tissues and are recorded on an image receptor
What is another name for non-particulate radiation?
Electromagnetic radiation
Describe energy transfer with EM radiation?
Transfer of energy thru space as a combination of electrical and magnetic fields
Is EM radiation best described by wave theory or quantum theory?
Actually EM radiation is best described by a combination of both wave and photons (quanta)
Why do we use a focusing cup when taking radiographs?
Due to the wave nature of EMR, EMR travels in all directions from its source, thus a focusing cup is used to direct the EMR toward the patient.
Define wavelength
The distance between 2 successive crests of troughs. Measured in meters, or in the case of x-rays, measured in angstroms
Define frequency
Number of oscillations, vibrations, waves, or cycles per second
How does velocity relate to wavelength and frequency?
velocity = wavelength x frequency
Does velocity of EMR in air vary?
NO! Velocity of all EMRs in air is the same (3x10^10 cm/sec)
How are energy and velocity related?
Energy and velocity are directly related, therefore an increase in in velocity results in an increase in energy
How are energy and wavelength related?
Energy and wavelength are inversely related, therefore an EMR with longer wavelength will have lower energy
