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Physics YEAR 1 and 2 > nuclear and particle physics > Flashcards

nuclear and particle physics Flashcards

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1
Q

what is meant by the unified atomic mass unit

A

1/12 of the mass of a carbon 12 atom. 1u=1.661x10^-27 kg

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2
Q

what is meant by the proton number

A

the number of nucleons inside the nucleus of the atom also known as the atomic number

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3
Q

deductions from the alpha particle scattering experiment

A

the vast majority of the mass of the atom is contained within a small volume called the nucleus

the nucleus has a positive charge

the nucleus of the atom is significantly smaller than the atom itself.

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4
Q

equate the energy lost to the electric potential energy at the distance of the closest approach

A

1/2mv^2=Qq/4π∑r

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5
Q

what is the strong nuclear force

A

acts between nucleons and holds the nucleus together against the electrostatic repulsion of the protons

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6
Q

what are the properties of strong nuclear force

A

-acts within the confines of the nucleus
-force acts between nucleons independent of charge
-provides a repulsive force between nucleons for distances of separation of around 0.5x10^-15
-it is attractive between distances of 3.0x10^-15 and 0.5x10^-15

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7
Q

is the relationship between nucleus size and nucleon number linear?

A

no, R=roA^1/3
ro=constan

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8
Q

calculate density

A

p=m/v

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9
Q

what is the equation for density of a nucleus

A

p=3m/4πr^3

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10
Q

what are fundamental particles

A

are particles that cannot be broken down into smaller components

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11
Q

what are hadrons

A

are particles consisting of a combination of quarks to give a net charge of zero or whole number. all experience the strong force

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12
Q

name two particles which are hadrons

A

neutrons and protons

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13
Q

what are leptons and two examples

A

fundamental particles. electrons and neutrinos

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14
Q

what are quarks

A

components of hadrons , and have a fractional electric charge. different types of quarks.
up, down and strange.

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15
Q

what is a neutrino

A

is a fundamental particle with almost no mass and zero charge. each neutrino has an antimatter particle called an antineutrino.

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16
Q

what is the weak nuclear force

A

felt by both quarks and leptons. It can change quarks from one type to another or leptons from one type to another is responsible for beta decay.

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17
Q

what is an antiparticle

A

is a particle of antimatter that has the same rest mass, but, if charged, the equal and opposite charge to its corresponding particle.

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18
Q

what two groups can subatomic particles

A

hadrons and leptons

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19
Q

what are antiparticles

A

the opposite charge to the associated particle

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20
Q

properties of quarks

A

spin, baryon number, lepton number, stangness and charm

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21
Q

the quark theory

A

up, down and strange quarks.

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22
Q

what is an alpha particle

A

is a particle comprising two protons and two neutrons ejected from nucleus during radioactive decay. it is identical to helium nucleus and is emitted due to its unusually high stability as a particle.

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23
Q

why did they do the alpha particle experiment in a vacuum

A

the alpha particles cannot travel too far without getting absorbed by the air.

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24
Q

what is a scintillator

A

when a high energy particle hits it, it gives out a flash of light.

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25
Q

how did the scattering experiment disprove the plum pudding model

A

alpha particles were passing through the gold leaf, meaning the majority of the atom was empty

some particles were deflected by an angle

some of the particles were deflecting backwards (more than 90º)

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26
Q

what were the inferences made about atoms after the scattering experiment

A

there is a large area of concentrated positive mass, which managed to repel the positive alpha particle.
there must also be neutrons because the protons couldn’t account for all the mass of the elements

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27
Q

what is the mass of a proton

A

1.673x10^-27KG

28
Q

what is the mass of a neutron

A

1.675x10^-27KG

29
Q

what is an alpha particle

A

comprised of two protons and two neutrons ejected from the nucleus during radioactive decay. it is identical to a helium nucleus and is emitted due to its unusually high stability as a particle.

30
Q

what is beta particle

A

high speed electron emitted from the nucleus during beta decay. it is produced when a neutron changes into a proton

31
Q

what is a gamma ray

A

form of electromagnetic waves, emitted from the nucleus during gamma decay.

32
Q

what is radioactive decay

A

the spontaneous and random decay of an unstable nucleus. into a more stable nucleus by the emission of alpha, beta and gamma radiation.

33
Q

why is radiation spontaneous

A

because it is not affected by external factors such as pressure and temperature or by chemical reaction.

34
Q

what happens when alpha, beta and gamma goes through oppositely charged plates.

A

beta bends toward the positive terminal
gamma is not effected
alpha bends towards the negative terminal.

35
Q

what is a beta-minus

A

a neutron in the nucleus breaks down into a proton under the influence of the weak nuclear force, and a beta minus particle and an electron antineutrino are emitted. a beta minus is an electron

36
Q

what is a beta plus

A

in a decay where a proton breaks down into neutron under the influence of the weak nuclear force. a beta plus particle and an electron neutrino are emitted. a beta plus is also know as a positron

37
Q

what is the elemental symbol for the an alpha particle

A

4
He
2

38
Q

what is the elemental symbol for a beta minus decay

A

0
e
-1

39
Q

what is the mass of an electron in terms of u

A

1/2000 u

40
Q

what is the constant ro equal to

A

1.2fm or 1.2x10^-15m

41
Q

why is an electron not attracted to the nucleus

A

the electron experiences the force in the direction of the nucleus, but the electrons velocity is at a right angle to the force, so the electron orbits.

42
Q

why are two positive charges not repulsive inside the nucleus.

A

the strong force. If they get close enough the strong force will allow them to exist together

43
Q

when the nucleus is in equilibrium, what is the strong for equal to?

A

the electrostatic repulsion

44
Q

how do you calculate mass defect

A

predicted mass - calculated mass

45
Q

how do you calculate Binding energy

A

e=mc^2
mass defect x speed of light^2

46
Q

in terms of e, what is the charge of an alpha particle

A

2e

47
Q

what is the range of an alpha particle

A

a few cm. 4

48
Q

what is the range of beta-

A

up to 1m

49
Q

what is the range of beta +

A

it will find another electron, and annihilate, so short

50
Q

what is the range of gamma

A

very long distance

51
Q

what stops alpha radiation

A

few mm of paper

52
Q

what stops beta

A

few mm of aluminium 4-5mm

53
Q

what stops gamma

A

lead, exponential curve, so many cm of lead.

54
Q

what is annihilation

A

when a particle and its corresponding antiparticle collide, they annihilate each other and their combined masses are turned into energy, producing a pair of gamma photons. The energy of the photons must equal to intial kinetic energy and rest mass energy.

55
Q

what is pair production

A

opposite of annihilation.
pair production is when one high energy photon spontaeneously turns into a particle-antiparticle pair

56
Q

what do exchange particles do

A

push and pull particles together

57
Q

what is the exchange particle in the electromagnetic forces

A

virtual photon

58
Q

whats the exchange bosons for the weak nuclear force

A

W+,W-,Zo

59
Q

what are baryons

A

particles containing three quarks

60
Q

what are mesons

A

hardrons containing a quark and an anti quark

61
Q

what baryon numbers do mesons have

A

0, because they are not baryons

62
Q

what is strangeness

A

fundamental property of matter, a quantum number. The strangeness of a strange quark of -1.
the antistrange number is 1.

63
Q

what are the six different types of quarks

A

up down, top bottom, strange charm

64
Q

why is beta minus decay governed by the weak nuclear force

A

when neutron decays into a proton, its constituent particles change from udd to uud
so one down quark changes into an up quark
only the weak interaction can result into quarks changing type so the decay of a neutron into a proton must be governed by the weak force.

65
Q

where do muons come from

A

cosmic rays

66
Q

what is the electron lepton number of a muon antineutrino

A

0

Physics YEAR 1 and 2 (24 decks)

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