Radiation Physics

Question 1

2 types of radiation

Answer 1

particulate and electromagnetic

Question 2

radiation

Answer 2

transmission of energy through space and matter

Question 3

radioactivity

Answer 3

process where unstable nucleus breaks down and emits energy

Question 4

diagnostic imaging in dentistry uses ___ radiation

Answer 4

electromagnetic radiation

Question 5

2 theories for EM radiation

Answer 5

quantum and wave

Question 6

as energy increases, wavelength ___

Answer 6

decreases

Question 7

as wavelength increases, frequency ___

Answer 7

decreases

Question 8

types of ionizing radiation

Answer 8

UV, x-rays, gamma rays

Question 9

types of non-ionizing radiation

Answer 9

radio, microwave, IR, and visible

Question 10

ionizing radiation

Answer 10

removes an electron from an atom

Question 11

function of oil in x-ray tube head

Answer 11

conducts heat away, preventing overheating

Question 12

parts of the x-ray tube

Answer 12

cathode, anode, and evacuated glass tube

Question 13

components of cathode

Answer 13

filament and focusing cup

Question 14

function of filament

Answer 14

produces electrons

Question 15

function of anode

Answer 15

convert KE into x-ray photons

Question 16

why is tungsten used in the anode

Answer 16

• high atomic # (efficient production)
• high melting point (withstand heat)
• high thermal conductivity (dissipate heat)
• low vapour pressure (maintain vacuum)

Question 17

3 things that help dissipate heat

Answer 17

• use tungsten (high thermal conductivity)
• tungsten is embedded in copper
• angle of target to central ray

Question 18

2 reasons for the evacuated tube

Answer 18

• prevent oxidation of filament

- prevent collision of e with gas molecules that would reduce the speed

Question 19

3 settings that can be changed by operator

Answer 19

• tube current (# of e)
• tube voltage (energy)
• timer (time)

Question 20

2 possibilities for bremsstrahlung radiation

Answer 20

• e is deflected, x-ray = KE of e

- e strikes directly on nucleus, x-ray = all KE

Question 21

when is the energy of the photon discrete

Answer 21

characteristic radiation

Question 22

6 factors that affect primary beam

Answer 22

1. exposure time
2. tube voltage
3. tube current
4. filtration
5. collimation
6. distance

Question 23

___% of KE to x-ray photon is converted into heat

Answer 23

99%

Question 24

higher Z = ___ efficiency

Answer 24

higher

Question 25

increasing exposure time results in

Answer 25

- n/c quality - increase quantity - it is proportional

Question 26

increasing tube voltage/potential results in

Answer 26

- increase quality - increase quantity - not proportional

Question 27

increasing tube current

Answer 27

- n/c quality - increase quantity - it is proportional

Question 28

increasing filtration

Answer 28

- increase quality - decrease quantity - no change to image quality

Question 29

increasing collimation

Answer 29

- decrease exposed volume - decrease scatter - increase image quality

Question 30

intensity is related to

Answer 30

the number of photons

Question 31

4 x-ray outcomes

Answer 31

1. coherent scattering 2. compton scattering 3. photoelectric absorption 4. penetration (no interation)

Question 32

intensity of beam is dependent on

Answer 32

- photoelectric absorption | - compton scattering

Question 33

coherent scattering

Answer 33

- not common - same energy - diff direction - NON-ionizing - no change to image quality

Question 34

compton scattering

Answer 34

- common - LOWER energy - diff direction - ionixing - LOWER image quality

Question 35

higher Z = ____ attenuation

Answer 35

higher

Question 36

enamel is the ___ attenuated

Answer 36

most

Question 37

more attenuation = what colour

Answer 37

white

Question 38

absorption of x-rays

Answer 38

- photoelectric effect - results in characteristic radiation - low E => no change in image quality