Definitions

Question 1

Define the terms proton number and nucleon number

Answer 1

Proton number refers to the number of protons in the nucleus (Z) it defines the element.
The nucleon number is the number of protons and neutrons in the nucleus.

Question 2

Define isotopes

Answer 2

Atoms with the same number of protons but different number of neutrons.

Question 3

Define the specific charge of a particle

Answer 3

The specific charge of a particle is the ratio of its charge to its mass, given in C/kg.

Question 4

Define antiparticles and name the antiparticles of protons, neutrons, electrons and electro-neutrinos

Answer 4

Antiparticles are identical to its particle counterpart but with opposite charge. Hence they have same mass and rest energy.

Protons → Antiproton
Neutron → antineutron
Electron → positron
electron neutrino → anti neutrino

Question 5

Define leptons

Answer 5

Leptons are fundamental particles (not made up by quarks)
They are not affected by the Strong Nuclear Force, they instead interact via the weak interaction and gravitational and electromagnetic forces.

Question 6

state the names of the 4 main leptons and their antiparticles

Answer 6

electron, e- → positron
muon, μ- → antimuon (highly unstable)
electron neutrino, ν (e) → electron anti neutrino (only take part in weak interactions)
muon neutrino ν (μ) → muon anti neutrino (only take part in weak interactions)

Question 7

State the properties of the lepton antiparticles

Answer 7

Opposite charge and lepton numbers when compared to the particle.

Question 8

State the significance of muons

Question 9

Define hadrons in terms of the strong nuclear interaction

Answer 9

Hadrons are particles that can feel the strong nuclear force. They are made up from quarks held together by strong interaction.

Question 10

state the names of the two classes of hadrons

Answer 10

There are two classes of hadrons:
• Baryon (3 quarks or 3 antiquarks) [can’t mix quarks and antiquarks]
• Mesons (quark and antiquark pair)

Question 11

State the significance of the proton

Answer 11

Most stable baryon and lightest
All baryons decay to protons and protons cannot decay as it would violate the conservation of baryon number

Question 12

State the significance of the pion and the kaon

Answer 12

Pions and kaons were discovered in cosmic rays and can be observed through a cloud chamber.
Kaons are unstable and decay into pions in a weak interaction. This takes long due to the strange quark which prolongs lifetimes.

The PION (most stable meson) is the exchange particle of the nuclear force. They are responsible for binding nucleons together (strong nuclear force)

Question 13

State the interaction through which strange particles are produced

Answer 13

Strange particles are produced through the strong interaction

Question 14

State the interaction through which strange particles decay

Answer 14

Strange particles decay through the weak interaction.

Question 15

State in which interaction strangeness is always conserved

Answer 15

Strong interactions

Question 16

State the 5 properties that are conserved in all particle interactions and the other property that is only conserved in the strong interaction

Answer 16

•Charge, Q
•Baryon Number, B
•Lepton Number, L
•Energy
•Momentum

[strangeness if strong interaction]

Question 17

State or deduce the combination of quarks and antiquarks required for given common baryons or mesons

Answer 17

Baryons are made from three quarks or three antiquarks, proton uud and neutron udd

Question 18

State the exchange particle for each of the 4 fundamental interactions

Answer 18

these are called gauge bosons

STRONG : pion between nucleons and gluons between quarks
WEAK: W+ (beta plus), W-(beta minus), Z0
ELECTROMAGNETIC: photon

Gravity is negligible
The theorised exchange particle for the gravitational force is the graviton, however, this has not yet been discovered

Question 19

Define the term ‘photoelectrons’

Answer 19

The electrons emitted from the surface of a metal upon the absorption of electromagnetic radiation.

Question 20

Define the term ‘threshold frequency’

Answer 20

The minimum frequency of incident electromagnetic radiation required to remove a photoelectron from the surface of a metal

Question 21

Define the term ‘work function of a metal’

Answer 21

The minimum energy required to release a photoelectron from the surface of a metal

Question 22

Define ‘stopping potential’ in the photoelectric effect

Answer 22

The potential difference required to stop photoelectron emission from occurring

Question 23

Define the electron-volt

Answer 23

The energy gained by an electron travelling through a potential difference of one volt

1 eV = 1.6 × 10-19 J [E= Q/V ]

Question 24

Define the terms ‘excitation’ and ‘ionisation’ in atoms

Answer 24

Excitation refers to the movement of an electron move up energy levels by absorbing protons.
Ionisation refers to when electrons are removed.

Question 25

Give an example of EM behaving as particles and an example of particles behaving as waves

Answer 25

Light interacts with matter, such as electrons, as a particle
-The evidence for this is provided by the photoelectric effect
Light propagates through space as a wave
-The evidence for this comes from the diffraction and interference of light in Young’s Double Slit experiment

Question 26

Examples of Baryons

Answer 26

protons and neutrons

Question 27

Examples of Mesons

Answer 27

Pions, Kaons, Gluons