Particles - A level Physics Edexcel

What is the order of the scientists in the history of the atom?

What is the order of the scientists in the history of the atom?

1) Thomson 2) Rutherford 3) Bohr 4) Chadwick

What did Thomson discover about particles?

He used cathode rays to theorise the plum pudding.

What did Rutherford discover about particles?

The Geiger Marsden experiment with gold foil showed atoms are mostly made up of empty space and the nucleus is charged.

What did Bohr discover about particles?

Electrons in orbitals, electrons have fixed energies

What did Chadwick discover about particles?

Neutrons in the nucleus

What are the quarks?

Up, down, charm, strange, top and bottom

What are the leptons?

Electron, muon, tauon, electron neutrino, muon neutrino and tau neutrino

What are the bosons (force carriers)?

Gluon, photon, Z boson and W boson

What is the charge on an up?

2/3

What is the charge on a down?

-1/3

What is the charge on a charm?

2/3

What is the charge on a strange?

-1/3

What is the charge on a top?

2/3

What is the charge on a bottom?

-1/3

What is the charge on an electron?

-1

What is the charge on an electron neutrino?

0

What is the charge on a muon?

-1

What is the charge on a muon neutrino?

0

What is the charge on a tauon?

-1

What is the charge on a tau neutrino?

0

What is the charge on a gluon?

0

What is the charge on a photon?

0

What is the charge on a Z boson?

0

What is the charge on a W boson?

+/- 1

What is the charge on a higgs boson?

0

What is the symbol of a tauon?

τ

What is the symbol for a muon?

μ

What does the standard model show?

Matter

How do anti particles compare with the standard model?

They have the same mass but opposite charge

What's the anti-particle of an electron?

Positron (e^+)

Whats the anti-particle of a muon?

Muon plus (μ^+)

Whats the anti-particle of a tauon?

Tauon plus (τ^+)

What are leptons?

Fundamental particles

What are hadrons?

Mesons and baryons so matter/antimatter that isn't lepton

What are mesons?

Quark: Antiquark pairs

Examples of mesons

Pions and Kaons

What are baryons?

3 quarks

Examples of baryons

Nucleons: Protons and Neutrons, lambda, sigma and xi

How do you figure out lepton numbers?

If it is a lepton, it has a lepton number of +1. If its not a lepton, it has a lepton number of 0. If its an anti-lepton, it has a lepton number of -1.

How are muons and tauons created and what are they like?

They are created in high energy collisions so are unstable and short-lived

How do you figure out baryon numbers?

Quarks have a baryon number of +1/3, antiquarks have a baryon number of -1/3 and leptons have a baryon number of 0

What is a proton made up of?

uud

What is a neutron made up of?

udd

Examples of particle detectors

Bubble chamber and geiger muller tube

Examples of particle accelerators

LINAC, cyclotron and synchrotron

What happens in a LINAC?

Charged particles in a vacuum are accelerated in a straight line by a high frequency alternating voltage

What is the acceleration in a LINAC due to?

Repulsive and attractive forces between tubes because of the alternating pd

What does increasing the length of the tubes in the LINAC mean?

Travel through the tubes is matched with the alternating pd

What does the length of the LINAC limit?

The max speed

What is the advantage of the LINAC?

It can accelerate greater masses than cylotrons and synchrotrons as these require particles to be bent by a magnetic field so are limited by the strength of the magnetic field

What happens in a cyclotron?

Charged particles are accelerated in a vacuum chamber by alternating voltage across the gap of two dees

What ends the path of a charged particle in a cyclotron?

Magnetic field

What is the advantage of the cyclotron over the LINAC?

It has a spiral path so the particles travel a greater distance so go to greater speeds than the LINAC

How is a circular path maintained in a cyclotron?

As the particles gain kinetic energy (relativistic issues E=mc^2) the strength of the magnetic fields and frequency of the electric fields are varied.

What shape is a synchrotron?

Donut (torus) rather than disc shaped

What type of accelerator is CERN?

Synchrotron

What does a bubble chamber consist of?

A large cylinder with a liquid (eg hydrogen) heated to just below its boiling point

How are particles detected in a bubble chamber?

Charged particles ionise the liquid, forming microscopic bubbles which reflect light when illuminated

In a bubble chamber, what is bubble density around a track proportional to?

A particle's energy loss

What is the equation for a curved path in a bubble chamber?

r=mv/Bq

What does the direction of a particle track in bubble chamber indicate?

Charge

What does the radius of a particle track in a bubble chamber indicate?

Mass, speed and momentum

What are Geiger muller tubes for?

Detecting ionising radiation

What does a Geiger muller tube consist of?

A chamber filled with inert gas. The chamber contains two electrodes with a high pd across them.

What happens when a particle and antiparticle pair collide?

They annihilate. This means that their mass is converted to energy, The opposite can happen - energy can be converted to a particle-antiparticle pair. This is called pair production.

What is the rest mass of an electron?

9.11x10^-31 kg which is the same as 0.51MeV/c^2

What is rest mass energy?

The energy required to make a particle from energy

What must be conserved in particle antiparticle acceleration?

Charge, momentum and energy

Define matter

Any object that has mass or volume (occupies space). Matter is usually classified in four states or phases: solid, liquid, gas and plasma

What are the three types of mass?

Inertial mass, active gravitational mass and passive gravitational force.

What is inertial mass?

A quantitive measure of an object's resistance to acceleration

What is active gravitational mass?

A measure of magnitude of the gravitational force which is exerted by an object

What is passive gravitational force?

A measure of magnitude of the gravitational force which is experienced by an object when interactive with another object

What is the atomic mass unit (u)?

1.661x10^-27 kg

What is Einstein's theory of special relativity?

1) The laws of physics are the same for all non-accelerating observers 2) The speed of light within a vacuum is the same no matter the speed at which an observer travels

Why do only charged particles leave tracks in particle detectors?

When a charged particle passes through a substance it causes ionisation and electrons are knocked out of atoms so the particle leaves a trail of ions as it goes

Why do charged particles in particle detectors follow a curved tracks?

A charged particle moving in a magnetic field will experience a force. This means that the particles are deflected by the magnetic field.

How does the radius relate to the momentum?

The larger the curve radius of a particle track, the greater the momentum

How do positive and negative particle curves compare?

Positive and negative particles curve opposite ways

How do you find out which particles are positive and which are negative on a particle detector diagram?

Use Fleming's left hand rule

Why do you see spirals on particle detector diagrams?

Interactions with the detector decrease the kinetic energy of the particle so the radius decreases as the particle loses kinetic energy

What is the source of the electric field in a LINAC?

A high frequency alternating potential difference

Why do the electrons travel with constant velocity in the cylinders in a LINAC?

The electrons 'drift' in the cylinders because there is no electric field inside the cylinders due to the shielding so no force acts on the electron in the electric field and Newton's 1st law says that if there is no resultant force acting on a body it will move at a constant velocity.

Explain why the cylinders in a LINAC gradually increase in length along the accelerator

The cylinders must get longer as the electrons speed up for the time inside the cylinders to be constant - the passage of the electron between drift cylinders is synchronized with the phase of the electric field

What is a pion plus made of?

An up and an anti-down

What is a pion minus made of?

A down and an anti-up

What is a neutral pion made of?

An up and an anti-up

What is a kaon plus made of?

An up and an anti strange

What is a kaon minus made of?

An anti up and a strange

What is a kaon neutral made of?

A down and an anti strange

Whats the atomic number?

The number of protons in the nucleus. Its the atomic number that defines an element - no two elements will have the same number of protons.

How does the atomic number tell you about the chemical properties of an atom?

In a neutral atom, the number of electrons equals the number of protons. The element's reactions and chemical behaviour depend on the number of electrons.

What does the mass number of an atom tell you?

How many protons and neutrons are in the nucleus

What is the equation for the force exerted on a current- carrying wire in a magnetic field perpendicular to the current?

F=BIl

What equation shows the force acting on a single charge particle moving through a magnetic field?

F=BQv

What are the uses of a cyclotron?

Cyclotrons can be used in medicine to produce radioactive tracers or high-energy beams of radiation for use in radiotherapy

What are cyclotrons made of?

A cyclotron is made up of two hollow semicircular electrodes with a uniform magnetic field applied perpendicular to the plane of the electrodes, and an alternating pd is applied between the electrodes

What is the kinetic energy equation including charge?

KE=QV

Define electrovolt

1 electrovolt is the kinetic energy carried by an electron after it had been accelerated through a pd of 1 volt

What is thermionic emission?

When you heat a metal, its free electrons gain a load of thermal energy. Give them enough energy and they break free from the surface of the metal - this is called thermionic emission. Once they've been emitted, the electrons can be accelerated by an electric field in an electron gun.