Particles

Question 1

What is the Thompson Model?

Answer 1

Atoms were spheres of positive charge with tiny negative electrons stuck in them like a plum pudding

Question 2

What were Rutherford’s experiments?

Answer 2

A stream of α particles where fired at thin gold foil, this was used to disprove Thompson’s model

Question 3

What did Rutherford’s experiments prove?

Answer 3

Most of the particles went through the foil = particles were mostly empty
Some particles deflected at large angles = positively charged nucleus
Some particles were deflected at obtuse angles = the nucleus must be much smaller than the atom

Question 4

What is the charge of an electron?

Answer 4

1.6x10-19 C

Question 5

How does Flemming’s left-hand rule relate to circular motion?

Answer 5

The force on a charged particle from a magnetic field always acts perpendicular to the particles direction causing circular motion
F = Bqv and F= mv^2/r

Question 6

What formula relates the momentum (or mass and velocity) of a charged particle in a magnetic field to the radius of its path?

Answer 6

r = mv / Bq
ρ = mv

Question 7

What’s a cyclotron?

Answer 7

A device made of 2 semicircular electrodes with uniform magnetic fields applied perpendicularly to the electrodes upon an electron using an alternating current

Question 8

How does a cyclotron work?

Answer 8

A p.d is induced across the electrodes and a particle is fired into it
P.d causes the particle to accelerate
The increases in speed cause the radius of the increase
The potential difference is reversed so that it continues to accelerate

Question 9

What’s an electron volt?

Answer 9

1ev= 1.6x10^-19 J
1J = 6.25x10^18 ev

Question 10

What’s a linac?

Answer 10

A linear particle accelerator

Question 11

How does a linac work?

Answer 11

Electrodes are connected to an alternating supply so the charge of the electrode constantly switches between + and -
The rate of alternation is timed so that the particle is always attracted to one electron and repelled by the other
The electron speeds up and to compensate for this the length between the electrons increases.

Question 12

How does an electron gun work?

Answer 12

Heat a negative metal electrode until thermionic emission occurs
Fire the electron at the cylindrical anode with a whole in it

Question 13

What are hadrons?

Answer 13

Non-fundamental particles made of quarks

Question 14

What are the two types of hadrons?

Answer 14

Baryons and Mesons

Question 15

What are baryons?

Answer 15

Protons and Neutrons ect… with baryon number 1

Question 16

What is the only stable baryon?

Answer 16

Proton, as the neutron can decay into a proton

Question 17

What are mesons?

Answer 17

Unstable hadrons with a baryon number of 0

Question 18

What are leptons?

Answer 18

Fundamental particles that cant be made any smaller

Question 19

3 maian types of letpons?

Answer 19

Electrons, Muons, Tau (the other 2 weird ones are basically just heavy electrons)

Question 20

What is a neutrino?

Answer 20

A particle that has no charge represented with ν “nu”

Question 21

What is the lepton rule for these particles?

Answer 21

They all have a lepton number of 1, but they are all counted separately

Question 22

What’s an antiparticle?

Answer 22

A particle with equal mass, but the reverse of the charge and lepton/baryon number

Question 23

What is the mass and energy equivalence formula?

Answer 23

E = mc^2

Question 24

What does the energy equivalence formula show?

Answer 24

That matter can be created from energy

Question 25

What is the rule for when matter is created?

Answer 25

When matter is created an equal amount of antimatter must also be created

Question 26

What is annihilation?

Answer 26

When a particle and antiparticle collide all matter is exchanged for energy

Question 27

What are quarks?

Answer 27

The building blocks for hadrons

Question 28

Types of quarks?

Answer 28

up, down, strange
top, bottom, charm

Question 29

What quarks are used to make protons and neutrons?

Answer 29

only the up and down quarks

Question 30

QUARK TABLE

Answer 30

QUARK TABLE

Question 31

What properties must be conserved in particle interactions?

Answer 31

Energy and momentum
Charge
Baryon Number
Lepton number

Question 32

How does particle detection work?

Answer 32

Charge particles leave a track of ionisation that can be detected and recorded

Question 33

How does a cloud chamber detect particles?

Answer 33

Using a supercooled vapour, ions left by the particles condense leaving tracks
Thicker traces mean more ionisation
ONLY SHOWS CHARGED PARTICLES

Question 34

How do bubble chambers detect particles?

Answer 34

Hydrogen is kept as a liquid above its boiling point by pressurizing it
Ionisation by charged particles causes a reduction in pressure in some parts causing bubbles

Question 35

How can magnetic fields be used in particle detection?

Answer 35

Magnetic fields cause a particle to deflect in circular motion.
Positive particles follow the opposite direction to Flemming’s left hand rule

Question 36

When do neutral particles show up?

Answer 36

Only upon decaying or interacting with a charged particle