Physics

Question 1

Define an Element? 2

Answer 1

elements cannot be broken down into simpler forms. I.e Hydrogen or carbon
Element is a substance whos atoms have the same atomic number.

Question 2

Define a compound?

Answer 2

two or more elements linked together chemically i.e water or oxygen

Question 3

Describe and define an Atom? 3

Answer 3

Smallest part of an element, which retains the chemical properties of the element.
Positively charges nucleus contains proton and neutrons.
Electrons - negative charge

Question 4

Define the Atomic Number? 2

Answer 4

Defines Chemical behaviour of the atom
Number of Protons in the nucleus which is the same as the number of electrons.
Carbon (Z) = 6

Question 5

Define a molecule? 2

Answer 5

smallest part of a compound which retains the chemical properties of that
compound

molecule comprises a number of atoms linked together e.g water is H2O.

Question 6

State the charge of a proton and electron

Answer 6

Proton = +1.602 x 10^-19 coulombs
Electron = -1.602 x 10^-19 coulombs.

Question 7

State the mass of a proton and electron?

Answer 7

Proton = 1.66 x 10-27kg

Electron = 9.11 x 10-31kg

Question 8

Define the mass/nucleon Number? 1

provide formula to calculate neutron number 1

Answer 8

Total number of protons and neutrons in an atom

N=A-Z}

Question 9

Define an isotope 2

Answer 9

Atoms with the same number of proton and electrons but different number of Neutrons.. same chemical properties. Different atomic mass. In part a radioactive variation of the element.

Question 10

State the number of e in each shell

k
L
M
N

Answer 10

k2
L8
M18
N32

Question 11

Define an electron volt

Answer 11

1 eV = 1.6 x 10-19 J

Question 12

Describe what happens when an electron is in an excited state 1

Answer 12

absorb energy via collision or em radiation

electrons may be shifted to a higher energy level
atom is unstable and described as being in an ‘excited state
electron will
soon (less than one microsecond) fall back to its original shell, at the same time releasing in the
form of EM radiation the energy that was originally absorbed

Question 13

Increase in atomic number can have what effect on Binding energy?1

Answer 13

Increase

Question 14

state two types of Attenuation = 1

Answer 14

scattering and absorption

Question 15

Define absorption 1

Answer 15

photon interacts with the atom and loses all of its energy to the atom

Question 16

Define scattering 1

Answer 16

photon interacts with the atom and is deflected, which may or may be accompanied
with a loss of energy

Question 17

Define Total linear attenuation coefficient 1

Answer 17

fraction of x-rays removed from a parallel beam of monochromatic radiation per unit
thickness of a homogeneous attenuator

Question 18

what two factors can effect total linear coefficient? 2

Answer 18

1 The area and material presented to the incoming x-ray photons i.e. high atomic number
materials have high number of electrons.

2 spacing between the atoms in the medium. A dense medium provides a higher
probability of attenuation then a less dense medium, even if the atomic number is the
same.

Question 19

Define HVT/L 1

Answer 19

thickness of a substance which will transmit exactly one-half of the intensity of
radiation incident upon it

Question 20

what HVT materials are used in radiography and radiotherapy? 2

Answer 20

we use aluminium to measure the HVTs, whereas in

therapy we use copper.

Question 21

What can Linear attenuation coefficient figures be used for? 1

Answer 21

radiation protection purposes

Question 22

Draw a graph showing the relationship between intensity and material thickness. 2

Answer 22

y- intensity

x - attenuator thickness

Question 23

what is the HVT of water 1

Answer 23

30 mm

Question 24

What is the HVT of lead 1

Answer 24

0.1 mm

Question 25

define the total mass attenuation coefficient and where is it used? 2

Answer 25

Total mass attenuation =
μ/p
linear attenuation coefficient/ density

radiotherapy

Question 26

With increasing energy the linear attenuation coefficient decreases. What happens to the HVT? 1

Answer 26

Increases

Question 27

define attenuation 1

Answer 27

gradual decrease in intensity as a beam passes through an absorbing material

Question 28

Define intensity

Answer 28

Intensity WM-2 = watts/area m-2

Question 29

What has a higher absorption coefficient bone or fat?

Answer 29

Bone

Question 30

State the unit of the attenuation coefficient

Answer 30

M-1 or per meter

Question 31

Define total mass absorption coefficient

Answer 31

Total mass absorption coefficient
This is defined as the fraction of the energy contained in the x-ray beam which is absorbed per
unit mass of the irradiated medium.