3.2.1.3 Particles, Antiparticles and Photons Flashcards
What is an antiparticle? What are its properties in relation to a particle?
An antiparticle is a matching opposite of a particle. It has: Same mass Same rest energy Opposite Charge Opposite Spin direction.
What is the symbol for a proton?
Symbol for a proton is p
What is the symbol for an antiproton?
The symbol for an antiproton is p with a line on the top.
What is the relative charge of an antiproton?
Relative charge = -1
What is the rest energy of a proton and an antiproton?
938.3 MeV
What is the symbol for a neutron?
The symbol for a neutron is an n.
What is the symbol for an antineutron?
The symbol for an antineutron is n with a line on the top.
What is the rest energy of a neutron and an antineutron?
939.6 MeV
What is the symbol for an electron?
e -
What is the symbol for a positron?
e +
What is the relative charge of a positron?
Relative charge = + 1
What is the rest energy of an electron and a position?
0.511 MeV
What is the symbol for a neutrino?
The symbol for a neutrino is Ve
What is the symbol for an antineutrino?
The symbol for an antineutrino is Ve with a line on the top.
What are the properties of a neutrino and an antineutrino?
Both have 0 relative charge.
Both has 0 Mass in Kg.
Both has 0 Rest energy in MeV.
What can infrared cameras be used for?
We can use them to observe objects in darkness.
What is light a small part of?
Light is a small part of the spectrum of electromagnetic waves.
What is the speed of light in a vacuum?
The speed of light in a vacuum, c, = 3.00 x 10^8.
What is the symbol for wavelength?
Lambda.
What is the unit for wavelength?
Metres, m.
What is the symbol for wave speed?
v.
What is the unit for wavespeed?
Metres per second, m/s.
What is the symbol for frequency?
f
What is the unit for frequency?
1/seconds, or hertz.
What is wavelength usually given in?
Nanometres.
How do you convert from nanometres to metres.
1 nanometre = 10^-9 metres.
What is the electromagnetic spectrum?
A continuous spectrum of all the possible frequencies of electromagnetic radiation.
What has the lowest wavelength on the electromagnetic spectrum?
Gamma Rays
What has the highest wavelength on the electromagnetic spectrum?
Radio waves
What has the lowest and highest frequency on the electromagnetic spectrum?
Gamma rays = highest frequency
Radio waves = lowest frequency.
What is the frequency of a wave?
The frequency of a wave is the number of complete waves passing a point in a second.
What is the wavelength of a wave?
The wavelength of a wave is the distance between two adjacent crests of a wave,
What happens if you increase the frequency of an electromagnetic wave?
The higher the frequency of an electromagnetic wave, the greater its energy.
What does at an electromagnetic wave consist of?
An EM wave consists of an electric wave and a magnetic wave which travel together and vibrate.
How do the electric and magnetic waves vibrate?
They vibrate at right angles to each and to the direction they are travelling.
They vibrate in phase with each other. The two waves reach a peak and are in sync.
What is emitted when a charged particle loses energy?
EM waves are emitted.
What happens when a fast moving electron loses energy?
It stops, or slows down, or changes direction.
What happens when an electron in a shell loses energy?
The electron moves to a different shell of lower energy.
What did Max Planck find out about EM waves when investigating the black body radiation?
He discovered that EM waves can only be released in discrete packets, or quanta.
How are EM waves emiited?
As short, discrete bursts of waves. Each burst leaves the source in a different direction.
What did Einstein Suggest about the discrete packets of EM waves?
He suggested that EM waves and the energy that they carry can only exist in discrete packets, called photons.
What is the photoelectric effect?
The emission of electrons from a metal surface when light is directed at the surface.
What are electromagnetic waves?
Oscillations of electric and magnetic fields.
What are photons made off?
Packets of electromagnetic waves.
What do EM waves carry?
They carry energy,
What do photons carry?
They carry packets of energy.
How is the energy carried by an EM wave affected?
Higher frequency = Higher energy.
What does the energy of a photon depend on?
Energy depends on the frequency.
What is a photon?
A photon is a packet of EM energy. This gives the idea of an “item” occupying a certain space, and not a continuum like a wave propagating in space.
How do photons travel?
Photos travel in one direction only.
What is a known fact about the energy of a single photon?
The energy of a single photo is “quantized” and measurable.
Give 1 equation which can be used to calculate the energy of a single photon.
Energy = Planck’s Constant x Frequency.
E = h x f
Where energy = Joules
Frequency = Hertz.
Give another equation which can be used to calculate the energy of a single photon?
Energy = (Planck’s Constant x Speed of Light) / Wavelength.
Where energy = Joules
Speed of Light = m/s
Wavelength = m/
What is the value and unit for Planck’s constant?
Planck’s Constant = 6.63 x 10^-34 Joule Seconds.
Unit = Js
What did Einstein show that is represented by his famous equation
Energy = mass x Speed of Light squared?
Einstein has shown that the mass of a particle increases the faster it travels, and that his famous equation related the energy supplied to the particle to increase its mass.
What is the rest mass of a particle?
The rest mass of a particle is the mass of its particle when it is stationery. This corresponds to rest energy locked up as mass.
What did Dirac say about annihilation and antiparticles?
Every type of particle has a corresponding antiparticle that annihilates the particle and itself if they meet, converting their total mass into photos.
What did Dirac predict about photons with sufficient energy?
Dirac predicted that a photon with sufficient energy passing near a nucleus or an electron, can suddenly change into a particle-antiparticle pair, which would then separate from each other.
What is the energy of a particle or antiparticle expressed as?
It is expressed in Mega - ElectronVolts. (MeV)
What is 1 MeV equivalent to?
1 MeV = 1.50 x 10 ^-13.
What is definition of 1 Electron-volt?
The energy transferred when an electron is moved through a potential difference of 1 volt.
Do moving particles have different values of rest mass?
Yes, because they have kinetic energy, which is an equivalent form of mass.
What did Einstein say about mass and energy?
He said that energy can turn into mass, and mass can turn into energy.
Energy and mass are an equivalent form of each other. They are not the same, but can be turned into each other.
What is pair production?
Pair production is when energy is turned into mass, into a particle-antiparticle pair.
When does pair production happen?
Pair production only happens when there is enough energy to produce the masses of the particle and antiparticle pair.
Why is an antiparticle always produced?
The corresponding antiparticle must always be produced to conserve quantities.
Describe proton pair production.
Fire two protons with a large amount of kinetic energy at each other (i.e. moving at a high speed), and you will end up with a large amount of energy at the point of impact.
This energy might be converted into more particles.
If an extra proton is formed, then there will always be an antiproton to go with it.
Why is proton pair production highly costly?
Protons repel each other, so it takes a lot of energy to make them collide. This is very expensive.
What happens to the energy supplied in proton pair production?
The energy supplied is released when they collide, so proton-proton collisions produce a lot of energy.
What is photon pair production?
Photon pair production is when a proton with enough energy has an electron-positron pair.
When does photon pair production tend to happen?
It tends to happen when a photon passes near a nucleus.
Why do the particles tend to move away from each other in opposite directions after they are produced?
They are in an applied magnetic field, and have opposite charges.
Which type of photons have enough energy to produce an electron-positron pair?
Only gamma ray photons have enough energy to do so
What is the minimum energy needs for pair production?
The minimum energy needs for pair production is the total rest energy of the particles that are produced.
Give 1 equation which can be used to calculate the minimum energy needed.
Minimum energy of photon needed = 2 x rest energy of particle type produced.
Give another equation which can be used to calculate the minimum energy needed for pair production?
Minimum energy of photon needed = Planck’s constant x Minimum frequency.
How do you convert from MeV to joules, and vice versa?
MeV to eV = x 10^6
eV to J = x 1.60 x 10^-19.
What is annihilation?
Annihilation is when mass (particle and antiparticle) is converted into energy.
What happens to all of the mass of the particles?
All of the mass of the particles and antiparticle gets converted into energy in the form of two gamma ray photons.
Why are two gamma ray photons always produced and move in opposite directions?
There are 2 produced and they move in opposite directions to conserve momentum.
What is the minimum energy of the photon produced for annihilation?
The interaction is between a particle and an antiparticle pair, which have a combined rest energy of 2E.
The two photons need to have a total energy of at least 2E for energy to be conserved.
Give 1 equation which can be used to calculate the minimum energy produced in pair production.
Minimum energy of photon produced = Rest energy of particle type annihilated.
Give another equation which can be used to calculate the energy produced in annihilation.
Planck’s Constant x Frequency = Rest energy of a particle type annihilated.
When does positron emission take place?
Position emission, or beta plus decay takes place when a proton changes into an unstable nucleus with too many protons.
What is emitted in beta-plus decay?
A positron and a neutrino is emitted.
