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Basic Physics Flashcards

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1
Q

What is beam intensity?

A

total amount of energy per unit area travelling per unit time

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2
Q

Does all electromagnetic radiation travel at speed of light in vacuum?

A

Yes

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3
Q

What are secondary electrons?

A

Are electrons produced during compton

Their range depends on density of material and initial energy

**The more energy the photoelectron receives the higher the scatter angle of the photon**

Recoil electrons in compton

  • Can only go forwards or sideways

Photons can be scattered in any direction

  • can be alpha or beta particles
  • ionising
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4
Q

How may types of radiation can radionuclides emit?

A

Alpha

Beta

Gamma

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5
Q

What is atomic number of tungsten?

What is its K edge ?

A

Atomic number = 74

K edge 70

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6
Q

What is atomic number of lead?

A

Atomic number = 82

K edge = 88

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7
Q

What is atomic number of iodine?

What is K edge?

A

Atomic = 53

K edge = 33

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8
Q

What is atomic number and K edge of barium?

A

Atomic = 56

K edge = 37

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9
Q

What is the mean energy of the x-ray beam relative to the operating kV?

A

Mean energy is approx 50% of operating kV

The operating kV is the max energy possible

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10
Q
A
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11
Q

What does K alpha radiation result from?

A

Electron falling from L to K shell

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12
Q

What does K beta radiation result from?

A

Electron falling from M to K shell

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13
Q

What effect does increasing tube current have on x rays and curve?

A

Increasing mA (tube current) increases NUMBER of electrons hitting anode and therefore number of x- rays

Double tube current = double amount of x rays

Increasing mA does not affect curve shape, just makes it go upwards increasing amplitude

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14
Q

How does increasing kV affect curve shape?

Known as Tube Potential

Potential = kV

A

Curve up and to the right

Increases:

  • number of x-rays
  • energy of electrons
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15
Q

What is tube output equal to?

A

= kV2

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16
Q

What qualities does tube filament have?

A

High melting point

High resistance

Low vapour pressure

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17
Q

Probability of photoelectric reaction?

A
  • Proportional to the Atomic number3
  • Inversely proportional to the kV3 (ie low energy event)
    • 1 / kV3
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18
Q

IsoBARS have same…

A

Mass number

different atomic number

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19
Q

Alpha Particles

What happens in decay?

A

Mass number decreases by 4

Atomic number decreases by 2

  • High energy and very damaging
  • Particles carry a charge of +2
  • Travel 0.1cm in TISSUES
  • Have energy of 4-7MeV
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20
Q

What is included in electromagnetic spectrum?

A
  • Gamma
  • X ray
  • UV
  • Visible light
  • Infrared
  • Microwave
  • Radio

X-rays produced by electron reactions

Gamma rays produced by nucleur reactions

  • Both cannot be distinguished by frequency and wavelength
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21
Q

What voltage passes through tube?

A

10V

10A

22
Q

What dictates chemical properties of element?

A

Electrons in outermost shell are responsible for chemical properties

23
Q

What is 1 MBq equal to?

A

1 million decays per second

24
Q

Inverse Square Law

A

Doubling of will reduce intensity by 1/4

The inverse square law states that the intensity of radiation emitted from a point source will reduce in intensity, proportional to the square of the distance from that point

25
Q

How it HVL calculated?

A

0.69/LAC

26
Q

Does electromagnetic radiation have a mass?

A

NO

All electromagnetic radiation travels at the speed of light in a vacuum

27
Q

What is definition of HVL?

A

The thickness of a material required to reduce the INTENSITY of a beam by half

HVL increases as a beam pass through materials

28
Q

Does increased kV result in less side scatter?

A

Yes

Therefore reduced kV results in more side scatter

29
Q

What is intensity equal to?

A

The total ENERGY per unit time and area

Increased filter thickness will reduce intensity

30
Q

What propoerties do isomers have?

A

Same atomic and mass numbers

Different half lives as they are metastable

31
Q

What effect predominates in low atomic number materials?

A

Compton

  • Air
  • Soft tissue
  • Water
32
Q

What effect predominates in higher atomic number materials?

A

Photoelectric

  • Bone
  • Contrast
33
Q

What is Crurie equal to?

A

3.7x1010 transformations per second

A bequerel is 1 transformation per second

Decay constant is inversley proportional to half life

34
Q

How is absorbed dose measured in Radiography?

A

Ionisation chambers

35
Q

How is radiation dose read out on electronic dosimeters?

A

Silicon diodes

36
Q

Film Badges

A

Calibrated with caesium source

Have open window for detection of beta particles

37
Q

What is atomic number equal to?

A

Just the number of Protons

38
Q

What is K edge of calcium?

A

K edge = 4

Most natural elements in the body have a low K edge

39
Q

What is speed of light?

A

3x108

40
Q

What is Mass attenuation coefficient unit?

A

m2/kg

cm2/g

41
Q

What is mean beam energy?

A

50% of the operating tube kV

42
Q

What is max photon energy equal to?

A

The operating kV

43
Q

What is the decay constant?

A

The fracttion of nuclei decaying per unit time

44
Q

What is accelerating voltage in x-ray tube?

A

60 - 120kV

45
Q

What determines physical properties of an atom?

A

Mass number

46
Q

Can protons with sufficient energy be forced into a nucleus?

A

Yes

As seen in cyclotron

47
Q

What is linear attenuation coefficient?

A

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

Depdendent on density

Units are cm-1 or mm-1

48
Q

Does a change in kV or mA affect characteristic energy peaks?

A

NO

Doesnt affect distribution of peaks or energy but does result in more characteristic radiation

49
Q

What happens in bremmstraglung?

A

Filament electrons penetrate K shell but get deflected by nucleus

Continuous spectrum graph only represents Bremmstrahlung

50
Q

What increases probability of compton?

A

High electron density

High physical density

51
Q

Does increasing the kV affect number of filament electrons produced?

A

NO

Just increases total amount of x-rays produced at the target

Physics (10 decks)

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