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Physics > Particle Physics > Flashcards

Particle Physics Flashcards

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1
Q

What was JJ Thompson’s Model

A

Plum-Pudding Model is a sea of positive charge with negative electrons randomly embedded in a uniform sea of positive charge

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2
Q

Describe Rutherfords Experiment in detail (PROCESS)

A

Narrow beam of alpha particles of same KE, emitted from radioactive source, targeted at thin piece of gold foil only a few atomic layers thick.

Alpha particles scattered by foil, and detected by a zinc sulfide screen on a microscope. Every time an alpha particle hit the fluorescent screen, a speck of light was produced. This microscope was rotated from 0 to 180 degrees behind the foil.
This was used to detect the number of particles deflected through each angle.

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3
Q

Describe Rutherfords Experiment (OBSERVATIONS AND CONCLUSIONS)

A

Most of the alpha particles passed straight through the gold foil (only 1 in 2000 were deflected)
=> suggests atom is mostly empty space, with most of the mass concentrated in a small region ( known as nucleus according to nuclear model)

Very Few alpha particles (1 in 10,000) were deflected through an angle of greater than 90 degrees
=> suggests that nucleus is positively charged, as positively charged alpha particles were repelled

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4
Q

How were Neutrons discovered?

A

Chadwick showed that alpha particles hitting the beryllium nuclei were knocking out neutrons from its nuclei.

Showed that neutrons carry no charge and exist in all nuclei except hydrogen.

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5
Q

What is the nuclear model of the atom?

And what is meant by a nucleon?

A

Nucleus containing positively charged protons and uncharged neutrons.

Nucleon refers to protons and neutrons

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6
Q

Define Nucleon/Mass Number and Proton/Atomic Number?

How can you calculate the number of neutrons in an atom?

A

Nucleon number refers to number of protons and neutrons in an atom

Proton Number of an atom refers for number of protons

Nucleon Number - Proton Number = No. of neutrons.

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7
Q

What is an isotope?

A

Isotope of an element have the same proton number but a different nucleon number.

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8
Q

What is 1 atomic mass unit?

A

1 / 12th the mass of a carbon-12 atom
1.661 x 10^-27 kg

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9
Q

What is the formula to determine Radius of a nucleus given Atomic Number?

What does the constant represent?

A

R = r0 (A^1/3)

Where,

r0 = 1.2 fm = 1.2 x 10^-15 m
R= radius of atom

r0 represents the atomic radius of a hydrogen atom, which is roughly the same as the radius of a proton.

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10
Q

Describe some characteristics of the nucleus
What is the approximate density of the nucleus?

A

Nucleus is:
1.Small in Volume
2. Large in Mass
3. Thus, Extremely Dense

Density ~ 10^17 kgm^-3

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11
Q

Why do nucleons of the same charge not move away from each other?

Which force keeps them together and why?

A

Nucleons of the same charge will exert large force of electrostatic force repulsion.

Their gravitational force of attraction is much smaller in magnitude than electrostatic repulsion.

Therefore,another force must keep them together.

Thus, the attractive strong nuclear force is a force which acts over a range of 1-2fm, and acts between ALL nucleons.

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12
Q

What is the range of attractiveness and repulsiveness of the SNF?

A

Strong Nuclear Force is
ATTRACTIVE between 0.5 to 3fm
REPULSIVE below 0.5 fm

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13
Q

What is the theory of antiparticles?

A

An antiparticle exists for every particle.
If an antiparticle and particle collide, the two will collide and annihalte.

The masses of both will be converted into high energy photons.

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14
Q

What are the features of an antiparticle?

A

Antiparticle has the opposite charge of the same magnitude as its corresponding particle.

Anti-particle has the same rest mass as the particle.

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15
Q

What is the antiparticle of an electron?
What is it’s mass and charge

A

Positron
Mass : 9.11 x 10^-31
Charge= +1.6 x 10^-19

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16
Q

What is the antiparticle of a proton?
What is the antiparticle for a neutron

A

Anti proton
Antineutron

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17
Q

What is the symbol for a neutrino?
What is the antiparticle of a neutrino and what symbol?

A

V
V with bar on top

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18
Q

What are the four fundamental forces, and when are they experienced

A
  1. Strong Nuclear Force (nucleons within range 0.5 to 3fm)
    Relative Strength (1)
  2. Electromagnetic force (static and moving charge particles in an electric or magnetic field infinite range )
    Relative Strength (10 ^ -3)
  3. Weak Nuclear Force (responsible for causing beta decay within unstable nuclei)
    Relative Strength (10^-6)
  4. Gravitational Force (experienced by all particles with mass)
    Relative Strength (10 ^-40)
19
Q

What is the Weak Nuclear Force (WNF)?

A

Force responsible for causing beta decay in unstable nuclei.

20
Q

What is a fundamental particle?

A

A particle which has no internal structure and is indivisible into smaller components.

21
Q

What are the fundamental particles?

A

Quarks, and Leptons (Electrons, Neutrinos, Muons)

22
Q

What are Hadrons?

How do Hadrons Decay?

List 4 Examples of Hadrons

A

Hadrons are particles and anti particles that ARE AFFECTED by strong nuclear force.
Any particle which consists of quarks is a hadron

Hadrons decay by the Weak Nuclear Force

Eg. Protons, Neutrons, Mesons, Baryons…
Antiprotons, Antineutrons, Anti-Mesons (there are many…)

23
Q

What are Leptons?

List three examples

A

Leptons are particles and anti-particles which ARE NOT AFFECTED by the Strong Nuclear Force.

Electrons, Neutrinos, and Muons
Positron, Antineutrino, Anti-Muons

24
Q

What happens when Hadrons or Leptons become charged?

A

If Hadrons/Leptons are charged, they will EXPERIENCE THE Electromagnetic Force.

25
Q

What are quarks/leptons and why are they fundamental particles?

A

Quarks and Leptons (Electrons, Neutrinos, Muons) are fundamental particles.

Any particle which contains quarks is called a Hadron

They are fundamental particles because they have no internal structure + they are indivisible.

26
Q

What is the standard model of elementary particles?

A

Consists of six quarks and their Six anti-quarks.

Up, Down, Charm, Strange, Top, Bottom
Anti-Up, Anti-Down, Anti-Charm, Anti-Strange, Anti-Top, Anti-Bottom

Their charges are fractions of e

27
Q

What is the charge of

Up Quark, Charm Quark, Top Quark?

A

+2/3e

28
Q

What is the charge of

Down Quark, Strange Quark, Bottom Quark?

A

-1/3e

29
Q

Which force keeps the individual quarks bounded together within the particle

A

Attractive Strong Nuclear Force
It can be so strong that it is not possible to separate the individual quarks.

30
Q

What quarks does a proton consist of?

A

U,u,d
A proton consists of three quarks - Up, Up, Down
The total charge: +e

31
Q

What quarks does a neutron consist of?

A

udd
Up, Down, Down

Total Charge: 0

32
Q

What are Baryons?

A

Any hadrons made with a combination of three quarks.

Protons and neutrons are baryons. So are antiprotons, and antineutrons.

Mesons are any hadrons made with a combination of a quark and anti-quark.

33
Q

What are neutrinos?

What is the function of neutrinos in beta-decay?

A

Fundamental particles that carry no charge and may have a tiny mass (less than millionth of an electron)

Electron Neutrinos and Electron anti-neutrinos ensure that mass is conserved during beta decay.

34
Q

What are the types of neutrinos (needed)

A

Electron neutrino, Electron Antineutrino

35
Q

What are the two types of Beta Decay?

A
  1. Beta+ Decay => when an unstable nucleus decays to release a positron, electron neutrino
  2. Beta- Decay => when an unstable nucleus decays to release an electron, electron antineutrino
36
Q

Describe Beta Minus decay

A

In an unstable nucleus..
TOO MANY NEUTRONS for stability…

A NEUTRON decays into a Proton, Electron, and an electron anti-neutrino

1n0 -> 1p1 + 0e-1 + Ve_ (bar on top)

Nucleon and Proton number conserved so charge is conserved.

37
Q

Describe Beta Plus Decay

A

In an unstable nucleus…
TOO MANY PROTONS for stability…

…a PROTON decays into a neutron, a positron, and an electron neutrino

1p1 -> 1n0 + 0e1 + Ve

Nucleon and Proton number conserved so charge is conserved.

38
Q

What happens to Quark Structure of a neutron during beta-minus decay?

what is the charge equation?

A

Down Quark of neutron changes into Up Quark

UDD (neutron) -> UUD (proton)

in-terms of charge

D -> U + 0e-1 + Ve_

39
Q

What happens to Quark Structure of a proton during beta-plus decay?

A

Up Quark of a proton changes into Down Quark

UUD(proton) -> UDD (neutron)

U -> D + 0e1 + Ve

40
Q

What is a Baryon?

A

Baryon is a hadron that consists of three quarks

41
Q

What is a Meson?

A

Mesons are hadrons made with a combination of a quark and an anti quark

42
Q

What is a Muon

A

Muon is a type of Lepton => Fundamental Particle
Same charge as an electron (-e)
Has >200x mass of an electron

43
Q

What is the energy equivalent of 1u (1 atomic mass unit)

A

931.3 MeV
(1.49008 x 10^-10 J)

Physics (2 decks)

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