Unit 1 Flashcards Preview

Physics 1 - Particles, quantum phenomena and electricity > Unit 1 > Flashcards

Flashcards in Unit 1 Deck (80)
Loading flashcards...
1
Q

What is an isotope

A

An atom with a different neutron number but equal proton number

2
Q

What is a nuclide

A

A species of nucleus with unique set of protons and neutrons

3
Q

What is meant by the specific charge of a particle?

A

What determines the ratio between the electrical and gravitational forces on the particle.

4
Q

Specific charge equation with units

A
Specific charge(Ckg^-1) 
= q(C) / m(Kg)
5
Q

What is the contents of an atom

A

A positively charged nucleus containing protons and neutrons which is orbited by electrons

6
Q

Wha does the electrostatic attraction do?

A

Hold the electrons in the atom

7
Q

What keeps protons and neutrons together and how does it work

A

The strong nuclear force overcomes the electrostatic force of repulsion between the protons in the nucleus and keeps the protons and neutrons together

8
Q

2 Strong nuclear force facts

A

Has a range of 3-4fm (3x10^-15m)

Has the same effect between two protons, neutrons, or one of each.

9
Q

Fact about the electrostatic attraction between two charged particles

A

Infinite range

10
Q

When do unstable nuclei occur, give a general point and the 3 requirements for instability and 1 for stability

A

Too many protons as too high repulsion force causing the forces to be unbalanced
P>n - unstable
P>83 - unstable
P

11
Q

Structure of an alpha particle

A

Two protons
Two neutrons
Helium nucleus

12
Q

Alpha decay of:

X
A
Y

A

X X-4 4
A —> B + a
Y Y-2 2

13
Q

Beta radiation consists of ____ and where what happens?

A

Electrons

A neutron changes into a proton

14
Q

Beta decay of
X
A
Y

A

X X 0
A —> B + β
Y Y+1 -1

+ antineutrino (emitted by the sun too)

15
Q

What is gamma radiation (4)

A

Em radiation emitted by unstable nucleus
Pass through thick metal plates
No mass/charge
Emitted by nucleus with too much energy following alpha/beta emission

16
Q

How to calculate wavelength

A

λ = c/f

17
Q

c=speed of light=?

A

3x10^8m/s

18
Q

The _______ doesn’t affect a _____

A

The electrostatic force doesn’t affect a neutron

19
Q

Em waves travel at ____ in a vacuum

A

3x10^8m/s

20
Q

1nm=?m

A

10^-9m

21
Q

Em waves are ______ waves

A

Transverse

22
Q

Em waves consist of electric and magnet waves which….(2)

A

Oscillate in field strength perpendicular to the direction of wave propagation
And in phase with eachother

23
Q

Em waves are emitted by _____ when…

A

A charged particle when it loses energy

24
Q

When does a charged particle lose energy (2)

A

When an electron is stopped, slows down, or changes direction

When an electron moves down a shell

25
Q

What is a photon

A

A packet of em waves

26
Q

What does a laser beam consist of

A

Photons of equal frequency

27
Q

What is meant by the power of the laser and how is it calculated

A

Energy per second transferred by the photons

Power of laser = nhf where n is the number of photons passing a fixed point each second

28
Q

Em waves in descending order of wavelength (state wavelength) and increasing frequency and radiation

A
Radio= >0.1m
Microwave = 0.1-1mm
Infrared = 1mm-700nm
Visible = 700nm-400nm
Ultraviolet = 400nm-10nm
X-rays = 1-10nm
Gamma rays = <1nm
29
Q

MeV to J conversion

A

1.6x10^-13

30
Q

Why doesnt the strong nucleur force affect anything outside the nucleus

A

Because it only has a range of 3-4fm which is only roughly the diameter of a nucleus so cannot affect anything beyond it as it is out of reach

31
Q

What are the four fundamental forces?

A

Gravity
Electromagnetic
Weak nuclear
Strong nuclear

32
Q

Describe how the strong nuclear force between two nucleons varies with the separation of the nucleons quoting suitable values for separation.

A

The strong nuclear force has a short range of 3-4fm and is an attractive force with separations from 3-0.5fm however at less than 0.5fm it becomes a repulsion force that acts to prevent protons and neutrons from pushing into each other

33
Q

Describe and name the process of PET (5)

A

Positron Emission tomography – positron rich isotope is used as a tracer through the blood
because it emits positrons into the brain which comes up against an electron
and they annihilate and emit two photons
which are picked up by detectors that trace the location
so they can see if blood is flowing in order to locate cancers etc…

34
Q

Where to positron rich isotopes come from

A

Do not occur naturally, manufactured by placing stable isotope in the path of a beam of protons, some of the nuclei absorb extra protons and become unstable positron emitters

35
Q

When does positron emission occur and what is emitted

A

Positron emission occurs when a proton changes into a neutron in an unstable nucleus with too many protons. A neutrino is also emitted

36
Q

Positron decay

A

X X 0
A —> B + β
Y Y-1 +1

+ neutrino

37
Q

What type of energy are photons

A

radiation energy

38
Q

What happens when a antiparticle and its corresponding particle meet

A

They annihilate, converting their total mass into two photons

39
Q

Why are there two photons produced during annihilation

A

two photons because momentum must be conserved not taken away

40
Q

Compare antiparticle to a particle

A

All quantum numbers/properties are opposite for example opposite charges, if charged, however equal rest masses

41
Q

What is meant by 1 electron Volt

A

energy transferred when an electron is moved through a PD of 1 volt (1JC-1)

42
Q

Pair production is where

A

A photon is converted into a particle and its antiparticle if it has enough energy

43
Q

Minimum energy of photon needed =

A

hfmin = 2E0

44
Q

Momentum =

A

mass*velocity

45
Q

If the force between two particles takes time to act the effect is carried by…

A

an exchange particle moving at finite speed

46
Q

What is the feynman diagram for the electromagnetic force between two protons

A

p–>p
p–>p
y (virtual photon)

47
Q

What is the virtual photon

A

the boson carrying the electrostatic repulsion between two positively charged protons

48
Q

Why it the photon virtual

A

Because it cannot be picked up by a detector without preventing interaction to occur

49
Q

What does the strong nuclear force do

A

Holds the neutrons and protons in the nucleus together

50
Q

What is the Feynman diagram for a neutrino-neutron interaction

A

Neutron—>Proton
Electron Neutrino—>Electron
W- boson
(Neutrino absorbs W- boson –> electron)

51
Q

What is the Feynman diagram for an antineutrino + proton interaction

A

Electron Antineutrino –> Positron
Proton –> Neutron
W+ boson
(Antineutrino absorbs W+ boson –> positron)

52
Q

Three facts about the W bosons

A

have a non-zero mass, very short range of 0.001fm, positively or negatively charged

53
Q

In Feynman diagrams, total charge is ____

A

always conserved

54
Q

What force do electrons and positrons use

A

Weak nuclear force

55
Q

What force do protons and neutrons use

A

Strong nuclear force

56
Q

When a W boson meets a (i) neutrino (ii) antineutrino, they change into…

A

(1) an electron

(2) a positron

57
Q

What is the Feynman diagram for beta decay

A

Neutron —> Proton
Electron antineutrino —> electron
W- boson

W- boson decays into an electron and an antineutrino

58
Q

What is the Feynman diagram for positron decay

A

Proton –> Neutron
Electron antineutrino –> Electron
W+ boson

W+ boson decays into a positron and neutrino

59
Q

What is K-capture?

A

In large atoms, the inner-most shell of electrons is the K-shell. Sometimes an electron in this K-shell is captured by the nucleus causing the emission of a neutrino and a decrease in atomic number

60
Q

What is electron capture?

A

Sometimes a proton in a proton-rich nucleus turns into a neutron as a result of interacting through the weak interaction with an inner-shell electron from outside the nucleus

(If arrow reversed then sign reversed)

61
Q

What is the decay equation for K-capture

A

E- + 1A1 —> 1B0 + v

e + p –> n + v

62
Q

What is the Feynman diagram for electron capture

A

Proton –> Neutron
Electron –> Neutrino
W+ boson

63
Q

What is electron-proton collision

A

At very high speeds, an electron can turn into a Proton via the exchange particle of the W- boson

64
Q

What is the Feynman diagram for Electron capture

A

Proton –> Neutron
Electron –> Neutrino
W- boson

65
Q

Compare the W boson to the virtual photon (3)

A

W boson has mass, charge, very short range, weak interaction

Virtual photon, no mass, charge, infinite range, electromagnetic interaction

66
Q

Where do cosmic rays come from

A

supernova

67
Q

Describe the changes that take place in a proton-rich nucleus when it emits a positron

A

a proton in the nucleus changes into a neutron and a positron and neutrino are created and emitted from the nucleus

68
Q

State two ways in which pair production of a positron and an electron differs from positron emission

A

positron emission uses isotopes not photons, pair production doesn’t emit a neutrino.

69
Q

How does the alpha particle energy spectrum show there are two particles present

A

the unstable isotope has split into two parts, the daughter nucleus and an alpha particle. The daughter nucleus causes a spike in the alpha particle energy spectrum which must be conserved as energy can only be distributed one way.

70
Q

Antiparticle Vs particle

Deflection by electric field

A

Opposite

71
Q

Antiparticle Vs particle

Deflection by magnetic field

A

Opposite

72
Q

Antiparticle Vs particle

Deflection by gravitational field

A

Same

73
Q

Antiparticle Vs particle

Mean lifetime

A

Same

74
Q

Why does a photon need a minimum energy and what happens if there is more than this minimum energy

A

To form rest masses of both particles

Particles have more kinetic energy

75
Q

Where were neutrinos discovered

A

In a nuclear reaction

76
Q

69nm to m

A

69x10^-9m

77
Q

How are particles places into hadrons or leptons (6)

A

Hadron: proton/kaon
Lepton: muon

hadrons affected by strong nuclear reaction and are made of quarks
Leptons are fundamental and do not experience the strong nuclear reaction.
Hadrons are divided into baryons and mesons.
Baryons three quarks, mesons quark anti-quark pair.

Similarities between groups all experience weak interaction and if charged the electromagnetic interaction. All have rest mass.

78
Q

Repulsion between electrons

A

4 electrons and a photon

79
Q

A proton (p) and an electron (e–) combine to form a

A

neutron and neutrino and W+ boson

80
Q

If arrow reversed in feynman diagram then

A

Change charge of boson