Matter and radiation

Question 1

What are the main constituents of an atom?

Answer 1

● Proton
● Neutron
● Electron

Question 2

What is meant by specific charge?

Answer 2

The charge to mass ratio:
Specific charge = charge / mass

Units C/kg.

Question 3

What is the specific charge of a proton?

Answer 3

Protons have charge +1.6 x10^-19 and mass
1.67 x 10^-27 kg

Specific charge = 1.6 x 10^-19/1.67 x 10^-27
= 9.58 x 10^7 C/kg

Question 4

What is the letter associated with a
proton number?

Answer 4

Z

Question 5

What is a nucleon?

Answer 5

A constituent of the nucleus: a proton or a neutron.

Question 6

What letter represents nucleon number?

Answer 6

A

Question 7

What is an isotope?

Answer 7

A version of an element with the same number of protons but a different number of neutrons.

Question 8

State a use of radioactive isotopes.

Answer 8

Carbon dating - the proportion of carbon-14 in a material can be used to estimate its age.

Question 9

What is the strong nuclear force?

Answer 9

The fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons.

Question 10

Describe the range of the strong force?

Answer 10

● Repulsive up to 0.5fm
● Attractive from 0.5-3fm
● Negligible past 3fm

Question 11

What makes a nucleus unstable?

Answer 11

Nuclei which have too many of either protons or neutrons or both

Question 12

How do nuclei with too many nucleons decay?

Answer 12

Alpha decay (emission of a helium nucleus formed of 2 protons and 2 neutrons).

Question 13

How do nuclei with too many neutrons decay?

Answer 13

Beta minus decay in which a neutron decays to a proton by the weak interaction (quark character has changed from udd to uud).

Question 14

How was the existence of the neutrino hypothesised?

Answer 14

The energy of particles after beta decay was lower than before, a particle with 0 charge (to conserve charge) and negligible mass must carry away this excess energy, this particle is the neutrino.

Question 15

What is meant by beta minus decay?

Answer 15

When a neutron turns into a proton, the atom releases an electron and an anti-electron neutrino

Question 16

What is an alpha particle?

Answer 16

A particle contains two protons and two neutrons, the same as a helium nucleus.

Question 17

What is an antiparticle?

Answer 17

For each particle there is an antiparticle with the same rest energy and mass but all other properties are the opposite of its respective particle.

Question 18

True or false:
‘Every particle has a antiparticle’

Answer 18

True

Question 19

What is the name of the antiparticle of an electron

Answer 19

Positron

Question 20

What is the antiparticle of π0 (pion with 0 charge) ?

Answer 20

π0, its antiparticle is itself.

Question 21

What occurs when a particle and antiparticle meet?

Answer 21

Annihilation:

The mass of the particle and antiparticle is converted back to energy in the form of 2 gamma ray photons which go in opposite directions to conserve momentum.

Question 22

What is pair production?

Answer 22

A gamma ray photon is converted into a particle-antiparticle pair.

Question 23

What is the minimum energy of a photon required to make a proton-antiproton pair?

Answer 23

2 x proton rest energy
2 x 938.257 = 1876.514 MeV

Question 24

Name the 4 fundamental forces?

Answer 24

● Gravity
● Electromagnetic
● Weak nuclear
● Strong nuclear

Question 25

The virtual photon is the exchange particle of which force?

Answer 25

The electromagnetic force.

Question 26

What type of particles are affected by the strong nuclear force?

Answer 26

Hadrons

Question 27

What is the exchange particle of the weak nuclear force?

Answer 27

The W boson (W+ or W-).

Question 28

What does the electromagnetic force act on?

Answer 28

It acts on charged objects, for example when a positively charged ball repels another positively charged ball.

Question 29

When does weak nuclear interaction occur?

Answer 29

When quark character changes (a quark changes into another quark), it affects all types of particles.

Question 30

Which properties must be conserved in particle interactions?

Answer 30

● Energy
● Charge
● Baryon number
● Lepton number
● Momentum
● Strangeness (only for strong interactions)

Question 31

What is a hadron?

Answer 31

Both baryons and mesons are hadrons, hadrons are made of 2 or more quarks held together by the strong nuclear force.

Question 32

What are the classes of hadrons?

Answer 32

● Baryons (three quarks)
● Mesons (1 quark, 1 antiquark)

Question 33

The pion and kaon are both examples of which class of particle?

Answer 33

Mesons

Question 34

The pion can be an exchange particle for which force

Answer 34

The strong nuclear force.

Question 35

What particle does a kaon decay into?

Answer 35

A kaon decays into a pion.

Question 36

Give some examples of baryons?

Answer 36

● Proton - uud
● Neutron - ddu

Question 37

What is significant about a proton?

Answer 37

● It is the only stable baryon
● All baryons will eventually decay into protons

Question 38

What are some example of leptons?

Answer 38

● Electron
● Muon
● Neutrino
● (the antiparticles of the above)

Question 39

What does a muon decay into?

Answer 39

An electron.

Question 40

What is the strangeness value of a strange quark?

Answer 40

-1

Question 41

True or false:
‘Strangeness is always conserved in a weak interaction’

Answer 41

False.

Strangeness is only conserved in the strong interaction, in weak interactions it can change by 0, -1 and +1.

Question 42

Complete the sentence:
Strange particles are produced through the_____________ and decay through the ____________.

Answer 42

Strange particles as particles that are produced through thestrong interaction and decay through the weak interaction.