Atoms + Electricity

Question 1

proportionality

Answer 1

relationship between 2 numbers

• direct: as one # increases, other # increases
  eg. circumference of circle depends on diameter
• indirect: as one # increases, other DEcreases

Question 2

units of measurement

Answer 2

length: patients in cm, xray tube to cassette in m
time: seconds

Question 3

atoms

Answer 3

building blocks of elements
- nucleus has protons + neutrons
- electrons orbit

atomic number = electrons + protons
- stable if protons + electrons are equal

electron binding energy:
- force of proton’s positive charge holding e- in orbit
- directly proportional
- as protons increase, e- increase -> increases distance of e- from nucleus -> e- binding energy lowers -> atom less stable
- higher atomic # = less stable

Question 4

ionization

Answer 4

e- leave orbit of unstable atom (‘boiling off’)

• atom now considered ionized and has positive charge
• first step of x-ray (boil off e- from filament of cathode)
• higher atomic weight = more effect on other elements
• ^ principle used in radiation safety + contrast studies

Question 5

isotopes

Answer 5

atoms w/ same atomic # (electrons + protons) but different atomic mass (neutrons + protons)
- …..so protons would be same, but neutrons differ

• useful for contrast media, nuclear medicine, oncology

Question 6

radioactivity

Answer 6

atoms in abnormal state of excitement from unstable nucleus (from imbalanced neutrons + protons)

• radioactive disintegration/decay = atom’s attempt to reach stability
• nucleus spontaneously emits particles + energy -> transforms into different, stable atom

Question 7

electromagnetic spectrum

Answer 7

2 types of energy:

1. electrical
2. electromagnetism

involves radiation + visible light

Question 8

particle wave theory

Answer 8

x-rays travel in straight waves (crests + troughs)
- wavelength (distance b/w 2 crests)
- frequency (# of waves per unit of time)
- frequency + wavelength inversely related (short WL = high frequency = high penetration, long WL = low frequency = low penetration)
- waves have amplitude

x-rays are particles
- ‘photons’ of pure energy
- smallest quantity of electromagnetic energy
- travel at speed of light

Question 9

photon energy

Answer 9

photons interact w/matter as though they are a particle
- photon particle carries a specific energy dependent on frequency
- energy + frequency directly proportional (energy doubles = frequency doubles)
- x-ray beam composed of photons carried by wave

Question 10

x-ray discovery

Answer 10

1895 by german wilhelm roentgen

• noticed cardboard screen coated in platinocyanide glowed
• x-ray name because unknown
• listed 12 unique properties

Question 11

12 properties

Answer 11

1. invisible
2. electrically neutral
3. no mass
4. speed of light (in a vacuum)
5. can’t be focused by lens (passes through lens unchanged)
6. form polyenergetic beam (multiple photon energies per exposure)
7. can be produced in a range of energies (kV)
8. travel in straight lines
9. cause fluorescence
10. cause chemical changes in radiographic/photographic film (either penetrating film/absorbed by film)
11. can be absorbed or scattered by tissues in body, can produce scattered and secondary radiation
12. can cause chemical and biological damage to living tissue