Particle Physics

Question 1

Name the three things conserved in nuclear reactions.

Answer 1

Conservation of mass-energy
Conservation of momentum
Conservation of charge

Question 2

Who first postulated the neutrino? Why?

Answer 2

Pauli. Momentum not conserved in beta decay. Neutrino had the missing momentum.

Question 3

Who named the neutrino? What is the symbol for the neutrino?

Answer 3

Enrico Fermi. v.

Question 4

What is the formula for the Cockcroft and Walton Experiment? What is the historical significance?

Answer 4

7Li3 + 1H1 –> 4He2 + 4He2 + Energy
First experimental verification of E=mc(2)
First transmutation of an atom using ARTIFICIALLY accelerated particles.

Question 5

What is the formula for the first transmutation of an atom with NATURAL accelerated particles?

Answer 5

4He2 + 14N7 —> 17O8 + 1H1

Question 6

What is an advantage of circular particle accelerators over linear particle accelerators?

Answer 6

Particles can achieve greater speeds/energies
They are more compact.

Question 7

What is pair production? Why are photons always produced in pairs when annihilation occurs? What is pair annihilation?

Answer 7

Particle and its antiparticle created from a gamma ray.
conserve momentum
A particle and its antiparticle annihilate to form a pair of photons.

Question 8

Why is the mass of 1H1 different from than the mass of the proton?

Answer 8

1H1 contains the mass of the electron.

Question 9

A proton may be classed as a hadron explain why?

Answer 9

Experiences strong nuclear force

Question 10

A proton may be classed as a baryon explain why?

Answer 10

baryons composed of three quarks

Question 11

State the four fundamental forces of nature in order of increasing strength. Give each of their ranges in brackets beside them.

Answer 11

Gravity (Infinite), Weak Nuclear Force(short), Electromagnetic(Infinite), Strong Nuclear Force(short)

Question 12

State the quark composition for a (a) proton (b) anti-neutron

Answer 12

u,u,d. anti-u, anti-d, anti-d

Question 13

In a circular accelerator how are the particles (a) accelerated (b) kept in circular path. (c) detected.

Why is the tube evacuated?

Answer 13

Voltage (for straight accelerator) Magnetic Fields and electric fields (for circular); Magnetic Field; fluorescence when particles hit a zinc sulfide screen

So that particles don’t collide with gas particles.

Question 14

Why are neutrinos hard to detect?

Answer 14

Very small mass and no charge

Question 15

Name the two families of subatomic particles and distinguish between them.

Answer 15

Fermion-Half integer spin. Subject to exclusion principle
Boson-Whole integer spin. -not subject -transmit a force

Question 16

Name the two families of fermion and distinguish between them.

Answer 16

Hadron-Made up of quarks. i.e. protons and neutrons
Lepton-Fundamental Particle. i.e. electrons, neutrinos

Question 17

Name the two families of hadrons and distinguish between them.

Answer 17

Baryon-3 quarks. i.e. proton, neutrons
Meson-Quark-antiquark. i.e. pi 0

Question 18

What is the main fundamental force experienced by neutrinos?

Answer 18

Weak Nuclear

Question 19

Name one fundamental particle subject to the strong nuclear force.

Answer 19

Quark

Question 20

Why must two positrons be accelerated to high speeds to collide?

Answer 20

To overcome forces of repulsion.

Question 21

what is antimatter?

Answer 21

Matter that has the same mass as another particle but opposite charge.

Question 22

What antimatter particle was discovered from cosmic rays in 1932? Give its symbol.

Answer 22

positron; e+

Question 23

What happens when a particle meets it antiparticle?

Answer 23

Pair annihilation occurs followed by creation of two photons.

Question 24

Construct all the possible quark combinations for the mesons.
Give a name and charge for each.

Answer 24

U + anti u = pi0 Charge: 0 Name: Pi-neutral
U + anti d = pi+ Charge: +1 Name: Pi-plus
d + anti u = pi- Charge: -1 Name: Pi-minus
d + anti d = pi0 Charge: 0 Name: Pi-neutral

Question 25

In the Cockcroft and Walton experiment why did most protons not split a lithium nucleus?

Answer 25

Atoms mostly empty space, protons pass straight through.

Question 26

Define photon. Which directions do the two photons travel after annihilation?

Answer 26

Packet of electromagnetic radiation.
Opposite directions.

Question 27

Who first postulated anti particles? Who discovered the positron?

Answer 27

Paul Dirac. Carl David Anderson.

Question 28

Give a use of pair annihilation.

Answer 28

A PET scanner

Question 29

Formulas for pair production and pair annihilation.

Answer 29

y ——> 0e-1 + 0e+1
0e-1 + 0e+1 —–> y + y

Question 30

State what particles each of the four fundamental forces affect and what there purpose is? What particles carry these forces?

Answer 30

Strong Nuclear: Neutron, Proton, Quark. Stability of Nucleus. Gluons.
Electromagnetic: Affects charged particles. Binds atoms. Photon.
Weak Nuclear: Affects all particles. Beta Decay. W and Z boson.
Gravity: Affects all particles. Holds Universe Together. Graviton Boson

Question 31

Who came up with the quark model in 1963? (2 answers)
Also who came up with the word quark?

Answer 31

Gell-Man and Zweig
James Joyce

Question 32

What are quarks?

Answer 32

The elementary particles that make up baryons and mesons.

Question 33

Difference between pair production and pair annihilation.

Answer 33

Pair production requires one gamma ray
Pair annihilation produces two gamma rays which share the energy.