C24 (Partcile Physics)

Question 1

Observations and Conclusions from Alpha particle experiment:

Answer 1

Most alpha particles passed straight through thin gold foil, very little scattering, meaning most of atom made empty space, most mass conc at centre in small region called the nucleus.

-Very few positive alpha particles were repelled when in close proximity to the nucleus, meaning nucleus has positive charge, in fact charge on nucleus is quantised (1.6 x 10^-19).

Question 2

Rutherford used alpha particles of KE 1.2 x 10^12J, with the idea of conservation of energy to calc the distance of the closest approach between an alpha particle and the gold nucleus.

The initial KE of alpha particle equal to what?

Answer 2

The initial KE of alpha particle = electrical potential energy at distance d

Question 3

Term nucleon refers to what

Answer 3

Term nucleon refers either proton or neutron.

Question 4

What’s the nucleon no. made up off

Answer 4

both protons and neutrons

Question 5

Isotopes

Answer 5

are nuclei of same element, have same no. protons but different no. neutron.

Question 6

Atomic Mass Units:

Answer 6

the masses of atoms and nuclear particles are often expressed in atomic mass units (u). The experimental value of 1u about 1.661 x 10^-27kg.

Question 7

Radius of nucleus given by:

Answer 7

R= r0 x cube root of A

-(where r0 = 1.2 femto metres (1fm = 1.0^-15m))
-The simplest nucleus, hydrogen, has A value of 1.
-The approximate mass of particle is its nucleon no. in atomic mass units.
-A the nucleon no. (protons and nucleons)

Question 8

What are the 3 forces within the nucleus

Answer 8

-The force acting between 2 point charges given by Coulomb’s law
-The force of gravity acting between 2 point masses, given by Newton’s law of Gravitation
-Strong nuclear force

Question 9

Nature of the Strong Nuclear Force

Answer 9

-According to Coulomb’s law, there’s extremely large repulsive force, and gravitational force between protons, not strong enough hold together. Other force that aids is the strong nuclear force.

-This force acts between all nucleons (a very short range force).

Question 10

Antimatter (Antiparticles):

Answer 10

-Every particle has corresponding antiparticle (if meet, destroy each other process annihilation, where their masses converted a high-energy pair of photons). Antiparticles have opposite charge to the particle and same rest mass.

Question 11

What’s the antiparticle of an electron

Answer 11

-Antiparticle of electron is positron (same mass, opposite charge).

Question 12

What are some other antiparticles (other then positron)

Answer 12

-Antiproton, Antineutron, Antineutrino

Question 13

How are antiparticles normally symbolised?

Answer 13

antiparticles symbolised by bar over the letter of original particle.

Question 14

What do fundamental forces explain?

Answer 14

These forces explain all known interactions.

Question 15

What is weaker nuclear force responsible for inducing?

Answer 15

The weak nuclear force is responsible for inducing beta-decay within unstable nuclei.

Question 16

What experiences strong nuclear force?

Answer 16

Experienced by nucleons

Question 17

What experiences electromagnetic force?

Answer 17

Experienced by static and moving charged particles

Question 18

Whats a result of weak nuclear force?

Answer 18

Responsible for beta-decay

Question 19

What experiences gravitational force?

Answer 19

Experienced by all particles with mass

Question 20

What’s the range for Fundamental forces

Answer 20

Electromagnetic and gravitational are infinite
Strong nuclear (10^-15m)
Weak nuclear (10^-18m)

Question 21

What’s a fundamental particles

Answer 21

A particle that has no internal structure, hence cannot be divided into smaller bits (quarks,electrons and neutrinos).

Question 22

What type categories are subatomic particles split into?

Answer 22

Hadrons and Leptons

Question 23

Hadrons

Answer 23

particles and antiparticles, affected by strong nuclear force (e.g protons, neutrons, and mesons). If charged, also experience electromagnetic force. Hadrons decay by weak nuclear force.

Question 24

Leptons

Answer 24

particles and antiparticles, not affected by strong nuclear force (e.g electrons, neutrinos, and muons). If charged, also experience the electromagnetic force.

Question 25

The CERN announced what?

Answer 25

CERN announced discovery of Higgs Boson (explaining why all particles have the property of mass).

Question 26

List the 2 fundamental particles that aren’t made of quarks

Answer 26

Fundamental particles, not made of quarks (e.g electron, neutrinos).

Question 27

Leptons examples

Answer 27

electrons, neutrinos, muons

Question 28

Hadrons examples

Answer 28

protons, neutrons, mesons

Question 29

What are hadrons made off?

Answer 29

Particles that are made of quarks

Question 30

Hadrons (Baryons):

Answer 30

Particles made of 3 quarks
E.g protons and neutrons

Question 31

Hadrons (Mesons):

Answer 31

particles made up of a quark and an antiquark.

Question 32

What’s the building blocks for all matter

Answer 32

Quarks
Leptons

Question 33

How many know quarks are there, that make up the standard model (name them)

Answer 33

Up
Down
Top
Bottom
Charm
Strange

Question 34

Each quark is unique and independent (all fundamental).

The main properties, interested in are: charge, baryon number, strangeness, spin.

What’s the charge for all the positive and negative quarks?

Answer 34

Positive +2/3

Negative -1/3

Question 35

What’s the relationship between the baryon number, the spin, and the strangeness?

Answer 35

Baryon no. the same for all quarks, (+⅓), so is the spin (+½) and the strangeness (0), except for the strange quark (-1).

Question 36

What’s a proton made out off, and what’s its charge?

Answer 36

Protons made of 2 up, 1 down (uud), the charge of up quark is +⅔e , charge down quark is -⅓e, therefore total charge is +1e.

Question 37

What are neutrons made of, and what’s their charge?

Answer 37

Neutron made up of 1 up, 2 down (udd), total charge is 0.

Question 38

Existence of neutrinos discovered when…

Answer 38

trying to explain beta decay, in terms of conservation laws (neutrinos are what make up for the missing energy, during beta decay).

Question 39

Out of the 3 types of neutrinos which one are we interested in?

Answer 39

interested in electron neutrino and electron antineutrino

Question 40

What happens in beta decay?

Answer 40

In beta decay, unstable nucleus decays into a proton, an electron, and an electron antineutrino.

Question 41

What’s emitted from Alpha radiation

Answer 41

Alpha radiation (emission of helium nuclei)

Question 42

What’s emitted from Beta radiation?

Answer 42

Beta radiation (emission either electrons or positrons)

Question 43

What is emitted from Gamma radiation?

Answer 43

Gamma radiation (emission of high-energy gamma photons)

Question 44

What is every type of radiation of result of?

Answer 44

Change that occurs to the neutrons or protons

Question 45

What are the 2 types of beta decay

Answer 45

Beta Plus Decay
Beta Minus Decay

Question 46

What is always conserved during beta decay

Answer 46

The nucleon no. A and proton (atomic) no. Z are conserved, as is total charge.

Question 47

What happens during beta-minus decay?

Answer 47

Neutron decays into a proton, electron and an electron antineutrino

Question 48

What happens during beta-plus decay?

Answer 48

In beta+ decay, a proton decays into a neutron, a positron and an electron neutrino.

Question 49

Quark transformation:

Answer 49

Beta-minus decay, neutron to proton

Beta-plus decay, proton to neutron