Basic Science & EM Radiation

Question 1

Atoms consist of:

Describing an atom

Answer 1

Nucleus: contains positive protons (p) and neutral neutrons (n)
Electrons: circle the nucleus within energy “shells”

A = mass number (p + n)
Z = atomic number (protons)
X = chemical symbol of the atom

Question 2

Rayleigh Scattering

Answer 2

Elastic Scattering

Question 3

Photoelectric interaction

Answer 3

Absorption

Question 4

Compton Scattering

Answer 4

Ineleastic scattering

Compt - You COMPROMISE on losing energy

Question 5

Increasing the x-ray tube kV increases output

Answer 5

By a factor of 2

Double kV = Output increased by a factor of 4

Question 6

Relationships of x-ray tube out for

kV (accelerating PD)
mA (tube current)
t (time)

Answer 6

kV = squared
mA = linear
t = linear

Question 7

Number of neutrons =

Answer 7

A - Z

Question 8

The neutrons and protons collectively called

Answer 8

Nucleons

Give the atom its mass

This isn’t the actual mass but that relative to other atoms.

Question 9

1 atomic mass unit (amu) =

Answer 9

1 atomic mass unit (amu) = 1/12 the mass of a carbon-12 atom

Question 10

Relative mass of protons, neutrons and electrons

Answer 10

Protons and neutrons = 1
Electrons = 0.0005 (5 x 10^-4)

Question 11

Name of each shell has a letter symbol and a maximum number of electrons it can hold calculated by

Answer 11

1 K 2 x 12 = 2
2 L 2 x 22 = 8
3 M 2 x 32 = 18

2 n^2

Question 12

Kinetic energy =

Answer 12

Kinetic energy = ½mv2

Question 13

The actual binding energy of electrons is expressed in

Answer 13

electron volts (eV) or keV (1keV = 1000 eV)

Question 14

Electrons have a binding energy that is the same as their

Answer 14

Actual negative energy

Binding energy = the positive energy required to release the electron from its shell = the negative energy released by electron when it is freed

Question 15

1 eV =

Answer 15

1 eV = 1.6022 x 10-19 joules

Question 16

The nucleus is composed of protons and neutrons. The protons repel each other via the

Answer 16

electrostatic force

Question 17

Nucleus is kept held together by the

Answer 17

strong nuclear force

Question 18

As the atomic number increases (i.e. the number of protons) you need more

Answer 18

neutrons are required to prevent the electrostatic forces pushing the protons apart and to keep the nucleus stable.

Question 19

EM radiation as waves

Answer 19

sinusoidally varying electric and magnetic field vector with the peaks pointing at right angles to one another and perpendicular to the direction the wave is travelling.

Question 20

Field Strength sinusoidally varies with

Answer 20

Distance and time

Question 21

1 ev =

Answer 21

1 ev = 1.6 x 10-19 J

Question 22

Intensity
The intensity (i.e. photon energy or field strength) is related to the characteristics of the wave by Planck’s constant.

E =

Answer 22

E = hf

E = photon energy
h = Planck’s constant (6.63 x 10-34 m2kg/s)
f = frequency

Question 23

If
E = hf
v = fλ

and assuming that the velocity is fixed (i.e. 1) gives you:

Answer 23

f = 1 / λ
E = h / λ

Question 24

Compton effect is interaction between a…

Answer 24

photon and a free electron

Question 25

Re: Compton effect
Does the wavelength change produced depend on the scattering material?

Answer 25

No

Question 26

Re: Compton effect
High energy radiation is scattered more than lower energy radiation?

Answer 26

No

Question 27

X-rays and gamma rays of a given energy interact in the same way in a low atomic number material?

Answer 27

Yes

Question 28

Re: Compton effect
Amount of scattering depend on material electron density?

Answer 28

Yes

Question 29

Re: Compton interaction
Probability of interaction in higher density materials?

Answer 29

Increases

Question 30

Re: Compton interaction
Photoelectric interaction can take place with any bound electron of an atom?

Answer 30

Yes

Question 31

The quantity of X-ray photons emitted from an X-ray tube:
Smaller or greater for tungsten than molybdenum target?

(Keeping everything constant)

Answer 31

Greater

Tungsten > molybdenum

Question 32

Quantity of X-ray photons emitted from an X-ray tube:

via the Bremsstrahlung mechanism, will be doubled if the mA is halved and the kV doubled

Answer 32

Doubled

Question 33

Linear attenuation coefficient (µ) is a constant that describes the

Answer 33

The fraction of attenuated incident photons in a monoenergetic beam per unit thickness of a material

includes all possible interactions including coherent scatter, Compton scatter and photoelectric effect

Question 34

The intensity of the beam at distance x (cm) within a material is calculated using the following equation

Answer 34

Ix=I0∙e−μx

Where Ix is the intensity at depth of x cm, I0 is the original intensity, and µ is the linear attenuation coefficient​.

Question 35

Total linear attenuation coefficient = mass attenuation x …..

has the units

Answer 35

mass attenuation coefficient x DENSITY

per metre
1/m
m^-1

Question 36

At energies greater than 50keV?

What effect is predominant in soft tissue?

Answer 36

Compton effect is predominant over the photoelectric effect in soft tissue

Question 37

The total filtration must be equivalent to at least

Answer 37

2.5 mm of Aluminium

Question 38

How will filtration affect the peak photon Energy?

Answer 38

Does not change the position of the peak, but will lower the total number at that energy

Question 39

Common for additional filtration to be made of..

Answer 39

Copper or Tantalum

Question 40

Isometric transition is the mechanism through which an excited nucleus emits

Answer 40

A gamma ray and returns to the ground state

Question 41

Following Beta emission, the atomic number of the radionuclide

Answer 41

Increases

Question 42

Photoelectric interaction can take place with

Answer 42

Any bound electron of an atom