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Physics A - Level > Particles and Radiation (1): Matter and Radiation > Flashcards

Particles and Radiation (1): Matter and Radiation Flashcards

1
Q

What does the term nucleon refer to?

A

A proton or neutron in the nucleus

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2
Q

What is the charge of an electron?

A
  • 1.6 x 10^-19
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3
Q

What is the charge of a proton?

A

+ 1.6 x 10^-19

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4
Q

What is the mass of a free proton?

A

1.673 x 10^-27

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5
Q

What is the mass of a free neutron?

A

1.675 x 10^-27

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6
Q

What is the mass of an electron?

A

9.11 x 10^-31

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7
Q

What is the mass of a nucleon bound in a nucleus?

A

1.661 x 10^-27

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8
Q

An uncharged atom contains equal numbers of…

A

protons and electrons

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9
Q

What is the definition of an isotope?

A

An atom of an element with the same number of protons but a different number of neutrons

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10
Q

What is the proton number also known as?

A

atomic number (bottom number on the periodic table)

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11
Q

What letter is used to represent the proton number?

A

Z

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12
Q

What is the term nucleon number/ mass number referring to?

A

The total number of neutrons and protons in an atom/ mass of the atom in relative units (the top number on the periodic table)

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13
Q

What does the term nuclide mean?

A

The type of nucleus that you are referring to

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14
Q

What letter is used to represent the nucleon/mass number?

A

A

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15
Q

How are nuclides labelled?

A

Using isotope notation e.g 12/6 C for carbon - 12

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16
Q

What is the definition of the specific charge of a charged particle?

A

Its charge divided by its mass

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17
Q

What are the units of specific charge?

A

Ckg^-1

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18
Q

Which particle has the highest specific charge?

A

the electron

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19
Q

What is the definition of a stable isotope?

A

One that will not undergo radioactive decay

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20
Q

What are the two types of force that act between nucleons in the nucleus?

A
  • The strong nuclear force
  • Electrostatic forces of repulsion
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21
Q

Which subatomic particles does the strong nuclear force act between?

A

neutrons and protons

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22
Q

Which subatomic particles does the electrostatic forces of repulsion act between? Why?

A

protons - as they are positively charged

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23
Q

What is the range of the strong nuclear force?

A

3-4 fm (femtometres, 10^-15)

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24
Q

What is the range of the electrostatic force of repulsion?

A

Infinite

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25
Q

How does the intensity of the electrostatic forces of repulsion fall off with distance?

A

The intensity falls off following the inverse square law, 1/d^2

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26
Q

At what value does the strong nuclear force become repulsive?

A

Values < 0.5 fm

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27
Q

Why does a -ve force mean attraction?

A

This is because 0 potential energy is at the infinity point, therefore, attraction means the objects are pulled together so their potential is more negative.

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28
Q

Why does a positive force mean repulsion?

A

This is because 0 potential energy is at the infinity point, therefore, the objects are moving closer to that infinity point so their potential is getting more positive.

29
Q

What is an alpha particle?

A

A helium nucleus

30
Q

When is an alpha particle emitted?

A

When the nucleus has too many protons, but it chucks out neutrons at the same time

31
Q

What is a beta particle?

A

A high speed electron/positron

32
Q

When is a beta(-) particle emitted?

A

When the nucleus has too many neutrons - a neutron is turned into a proton and electron (+ antineutrino)

33
Q

When is a beta(+) particle emitted?

A

When the nucleus has too many protons - a proton is turned into a neutron and positron (+ neutrino)

34
Q

What is gamma radiation?

A

EM radiation

35
Q

When is gamma radiation emitted?

A

By an unstable nucleus with too much energy that has already emitted an alpha or beta particle

36
Q

In a vacuum what is the speed of an EM wave?

A

3.00 x 10^8 ms^-1

37
Q

What is the equation for the wavelength of EM waves?

A

(lambda) = c/f

38
Q

What are the 7 types of EM waves in order and their wavelength ranges?

A

RADIO WAVES
>0.1m

MICROWAVE
0.1m -> 1mm

INFRARED RADIATION
1mm -> 700nm

VISIBLE LIGHT
700nm -> 400nm

UV RADIATION
400nm -> 1nm

X-RAYS
10nm -> 0.001nm

GAMMA RAYS
<1nm

39
Q

What are EM waves emitted by?

A

Charged particles when they lose energy

40
Q

When are EM waves emitted?

A
  • When a fast moving electron is stopped, slowed down or had its direction changed
  • When an electron in a shell of an atom moves to a different shell of a lower energy
41
Q

What is the definition of a photon?

A

A photon is a quantised/discrete packet of EM waves

42
Q

What is the definition of the Photoelectric Effect?

A

The emission of photoelectrons from the surface of a metal when light is shone on it

43
Q

What is the equation for the energy of a photon?

A

E = hf

44
Q

What is the value of Planks Constant?

A

6.63 x 10^-23 Js

45
Q

What is the equation for the power of a laser beam?

A

Power/energy per second of the beam = nhf

n - the number of photons in the beam passing a fixed point each second

46
Q

What happens when matter and antimatter meet?

A

EM radiation is released

47
Q

What are three characteristics of antiparticles?

A
  • They annihilate the particle and itself if they meet, converting their total mass into photons
  • has exactly the same rest mass as the particle
  • has exactly opposite charge to the particle if it has charge
48
Q

What did Einstein prove with his equation E = mc^2

A

That when a particle is stationary, its rest mass, m0, corresponds to its rest energy m0c^2 locked up as mass.

49
Q

What did Dirac predict?

A

The existence of antiparticles which would unlock their rest energies

50
Q

What is annihilation?

A

When a particle and antiparticle pair annihilate to produce two photons that are expelled outwards with equal energy and on opposite directions to conserve momentum.

51
Q

What is pair production?

A

When 1 photon interacts with a large mass/ catalyst particle e.g an atomic nucleus a particle-antiparticle pair will be produced. The nucleus absorbs the kickback that the photon experiences so that momentum is conserved.

52
Q

What is the definition of 1 eV?

A

The energy transferred when an electron is accelerated across a potential difference of 1 V

53
Q

How do you convert from eV to J?

A

E = QV

V - eV
Q - charge on the electron

54
Q

What is the equation that links the energy of the photons with the energies of the particle-antiparticle pair in annihilation?

A

2hf = 2mc^2

55
Q

What is the equation that links the minimum energy of the photons with the rest energies of the particle-antiparticle pair in annihilation?

A

2hf (min) = 2E0

E0 - Rest energy of the particle/antiparticle

56
Q

What is the equation that links the minimum energy of the photon with the rest energies of the particle-antiparticle pair in pair production?

A

hf (min) = 2E0

E0 - Rest energy of the particle/antiparticle

57
Q

What is the definition of a Boson/exchange particle?

A

The undetected particles that carry momentum and energy between the particles experiencing the force

NB: each fundamental force has its own exchange particle

58
Q

What is the boson that mediates the strong nuclear force interactions?

A

Gluon

59
Q

What is the boson that mediates the weak nuclear force interactions?

A

W+/- or Z+

60
Q

What is the boson that mediates the electromagnetic force between two charged particles ?

A

virtual photon

61
Q

Where does the weak nuclear force interact? Between what?

A

Acts in the nucleus between all particles, specifically leptons e.g electrons, neutrinos etc. and uncharged particles

NB: the force can attract or repel

62
Q

Which force is responsible for radioactive decay?

A

Weak nuclear force

63
Q

When does electron capture occur?

A

When a nucleus is proton rich

64
Q

Describe the process of electron capture?

A

There is a small, but still possible, probability that an electron in the lowest energy level can be found inside the nucleus. If this happens a proton turns into a neutron as a result of a weak interaction with this electron. The W+ boson mediates this interaction and a neutron an electron neutrino is produced.

65
Q

What are the rules when drawing Feynman diagrams?

A
  • Straight line - represents a particle
  • Squiggly line - represents bosons
  • The charge, and all other quantum numbers, must be conserved at each junction
  • Attraction and repulsion is visually the same on a Feynman diagram it is only the particles that are different
  • Time progresses upwards
  • The direction of lines does not show the direction of the particles
66
Q

What is a life application of annihilation? Explain?

A

PET scanners - A positron emitting isotope is injected into the blood stream and some of it reaches the brain. The positrons travel a few mm at most before they are annihilated by an electron producing two gamma photons as a result. The detectors connected to computers outside the body sense the photons emitted and are, therefore, able to build up an image from the signals of the brain.

67
Q

Write the decay equation for electron capture

A

p + e- (W+) -> n + electron neutrino

68
Q

Describe the Feynman diagram for an electron-proton interaction?

A

Same as for electron capture except a W- boson mediates the interaction which goes from the electron to the proton

69
Q

Write the equation for an electron-proton interaction

A

p + e- (W-) -> n + electron neutrino

Physics A - Level (20 decks)

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