Physic Basics

Question 1

what are radiographs

Answer 1

images produced by x-rays passing through an object and interacting with a receptor

Question 2

what do the different shades of grey on a radiograph correspond to

Answer 2

how dense the tissue it has passed through is

Question 3

what are the common intraoral radiographs

Answer 3

periapical
bitewing
occlusal

Question 4

what are the common extraoral radiographs

Answer 4

panoramic
lateral cephalograms

Question 5

what are x-rays a form of

Answer 5

electromagnetic radiation

Question 6

what is electromagnetic radiation

Answer 6

flow of energy created by simultaneously varying electrical and magnetic fields

Question 7

what are the properties of electromagnetic radiation

Answer 7

no mass
no charge
always travels at speed of light
can travel in vacuum

Question 8

how do you calculate wave length

Answer 8

the length of the cycle divided by how many sine waves there are

Question 9

how do you calculate frequency

Answer 9

cycles divided by the amount of time its taken

Question 10

what is frequency and how is it measured

Answer 10

how many times the waves shape repeats per unit time and measured in hertz

Question 11

what is wavelength and how is it measured

Answer 11

the distance over which the wave’s shape repeats measured in metres

Question 12

what is the calculation of speed

Answer 12

speed = frequency x wavelength

Question 13

how does energy move in electromagnetic radiation

Answer 13

via photons

Question 14

what are the types of x-ray

Answer 14

hard and soft

Question 15

what are hard x-rays

Answer 15

able to penetrate through human tissues

Question 16

what are soft x-rays

Answer 16

easily absorbed

Question 17

what separates x-rays from gamma rays

Answer 17

x-rays are man made

Question 18

what is ionisation

Answer 18

displacement of electrons from atoms

Question 19

how are x-rays produced

Answer 19

electrons are fired at atoms at very high speeds and when they collide the kinetic energy of the electrons is converted to electromagnetic radiation and heat - the x-ray photons released are aimed at the subject

Question 20

what do atoms consist of

Answer 20

protons
neutrons
electrons

Question 21

what is the relative charge, mass and location of a neutron

Answer 21

charge - 0
mass - 1
nucleus

Question 22

what is the relative charge, mass and location of a proton

Answer 22

charge - +1
mass - 1
nucleus

Question 23

what is the relative charge,, mass and location of an electron

Answer 23

charge - -1
mass - 0
shells

Question 24

what does the atomic number relate to

Answer 24

number of protons

Question 25

what does the mass number relate to

Answer 25

the number of protons and neutrons

Question 26

what is the most inner shell in an atom called

Answer 26

K - then proceeds through the alphabet from K

Question 27

how do you calculate the maximum number of electrons a shell can hold

Answer 27

2 x the shell number squared

Question 28

how are electrons held within their shell

Answer 28

electrostatic force

Question 29

what is the binding energy

Answer 29

the energy required to exceed electrostatic force (eg remove an electron from its shell)

Question 30

where is the electrostatic force greatest

Answer 30

the shells closest to the nucleus when there is a higher atomic number (aka more protons)

Question 31

how does an electron move to a more outer shell

Answer 31

energy that equals the difference in the binding energies of the two shells

Question 32

how does an electron move to an inner shell

Answer 32

energy is released

Question 33

what two values do you need to be able to calculate the energy needed to move an electron

Answer 33

binding energy of atom A binding energy of atom B

Question 34

what are the x-ray equipments for dental x-ray units made up of

Answer 34

tubehead collimator positioning arm control panel circuitry

Question 35

what is current

Answer 35

the flow of electric charge usually by movement of electrons - measured in amps

Question 36

what are the two forms of current direction

Answer 36

direct current - constant unidirectional flow alternating current - flow repeatedly reverses direction

Question 37

what is an alternating current cycle

Answer 37

the reverse and reverse back time (eg mains electricity)

Question 38

what does x-ray require the current to do

Answer 38

be flowing in one direction

Question 39

since x-rays are powered by mains electricity which is AC but x-rays require DC how does this come about

Answer 39

X-ray units have generators that modify the AC so it mimics a constant DC

Question 40

what is rectification

Answer 40

X-ray units have generators that modify the AC so it mimics a constant DC

Question 41

what is voltage

Answer 41

difference between negatively charged points in one place and positive in another aka potential difference

Question 42

what voltages does x-ray units require

Answer 42

high as 10s of thousands of volts one as low as 10 volts

Question 43

how do we get two difference voltage values from mains (240) voltage

Answer 43

through the use of transformers

Question 44

what are transformers

Answer 44

alter the voltage and current from one circuit to another

Question 45

how many transformers are required for an x-ray unit

Answer 45

mains - x-ray tube (cathod-anode) mains - filament

Question 46

what two transformers are there

Answer 46

step-up transformer which increases the voltage step down transformer which dcreases the voltage

Question 47

what is x-ray beam made up of

Answer 47

millions of photons directed in a same general direction

Question 48

what is x-ray beam made up of

Answer 48

millions of photons directed in a same general direction but they diverge away from x-ray source and do not travel parallel

Question 49

what is the x-ray beam intensity

Answer 49

quantity of photon energy passing through a cross-sectional area of the beam per unit time

Question 50

how can you increase intensity of an x-ray

Answer 50

increasing number or energy of photons

Question 51

how does divergence of x-ray beam affect the dose given

Answer 51

the further away, dose decreases

Question 52

what is the inverse square law

Answer 52

the intensity of the x-ray beam is inversely proportional to the square of the distance between the x-ray source and the point of measurement (doubling distance = quarter dose)