Particles And Radiation Flashcards
What is a nucleon?
A nucleon is a neutron or proton in the nucleus
What is the mass of a proton or neutron
- 27
1. 67 x 10 Kg
What is the charge of a proton?
-19
+1.6 x 10 C
What is the mass of an electron?
- 31
9. 11 x 10 Kg
What is the charge of an electron?
- 19
- 1.6 x 10 C
What is an isotope?
Isotopes are atoms with the same amount of protons but a different amount of neutrons
What is the nucleon number?
The total number of protons and neutrons in the atom
What is the proton number?
The total number of protons in the atom
What is a nuclide?
A nuclide is each different type of nucleus an element can have eg carbon-12 , carbon -14
What is specific charge?
The specific charge of a charged particle is defined as its charge divided by its mass
What force is responsible for preventing atoms from disintegrating?
The strong nuclear force as it overcomes the electrostatic forces of repulsion between protons in the nucleus.
Is the strong nuclear force an attracting or repulsive force?
It’s both at distances of 3-4 femtometres it is an attractive force to overcome the electrostatic forces of repulsion between protons in the nucleus. However at distances below 0.5 fm it is a repulsive force to prevent protons and neutrons squashing each other.
What is an alpha particle?
An alpha particle consists of 2 protons and 2 neutrons
What is a beta particle?
A beta particle is a fast moving electron
What is alpha radiation?
The emission of alpha particles from a radioactive substance, it has the general equation:
A A-4 4
X ——> Y + a
Z Z-2 2
What is beta radiation?
Beta radiation is the emission of a fast moving electron from an unstable nucleus, it has the general equation:
A
X
A
What is gamma radiation?
Gamma radiation is electromagnetic radiation emitted by an unstable nucleus, it has no mass or charge and can pass through thick metal plates. It is emitted by a nucleus with too much energy following alpha or beta decay.
What is the speed of light?
8
3 x 10 m/s
What do electromagnetic waves consist of?
Electromagnetic waves consist of a magnetic and electrical wave travelling together and vibrate at right angles to each other and the direction they are travelling. They also travel in phase with each other as they both reach their peaks at the same time.
What is the wavelength range of gamma waves?
< 0.1 no
What is the wavelength range of radio waves?
> 0.1 m
What is the wavelength range of infra red waves?
1mm - 700nm
What is the wavelength range of x rays?
10nm - 0.001 nm
What is the wavelength range of ultra violet waves?
400nm - 1nm
What is the wavelength range of microwaves?
0.1m - 1mm
What is the wavelength range of visible light?
700nm - 400nm
Electromagnetic waves are emitted when a charged particle loses energy give two examples of when this can happen:
- a fast moving electron being stopped, slowed down or changes direction
- an electron moving down a shell from its excited to ground state
What is a photon?
A photon is a packet of electromagnetic waves
Photon energy =
E = hf
What does a laser beam consist of?
A laser beam consists of photons of the same frequency
The power of an energy beam =
nhf
Where n is the number of photons in the beam passing a fixed point per second.
How does a PET scanner work?
A positron emitting isotope is administered to the patient, some of it will reach the brain via the bloodstream. Each positron travels only a few mm before meeting an electron where they annihilate each other. The two gamma photons produced in annihilation are then sensed by detectors and an image of the brain can then be built up.
What is positron emission and when does it occur?
Positron emission takes place when a proton changes into a neutron in an unstable proton heavy nucleus. In addition to the positron being emitted a neutrino is emitted.
How are positron emitting isotopes made?
They are manufactured by placing a stable a stable isotope in liquid or solid form in a path of a beam of protons. Some of the nuclei in the substance absorb extra protons and become unstable positron - emitters
What three things did Dirac predict about antimatter?
He predicted that there is an anti particle to every particle that:
- has exactly the opposite charge to its corresponding particle if it has a charge
- annihilates the particle and itself when they meet converting their total mass into photons
- has exactly the same rest mass as the particle
Dirac predicted pair production p what is pair production?
Pair production states that a photon with sufficient energy passing near a nucleus or an electron can suddenly change into a particle - antiparticle pair which then separate from each other
1 MeV to joules
- 13
1. 6 x 10 J
What is an electron volt?
One electron volt is defined as the energy transferred when one electron is moved through a potential difference of 1 volt
What is annihilation?
Annihilation occurs when a particle and corresponding anti particle meet and their mass in converted into radiation energy. Two photons are create in this process.
What is the formula for the minimum energy of each photon produced in annihilation?
hf min = E0 (The rest energy of the particle)
What is pair production?
In pair production a photon creates a particle and corresponding antiparticle and vanishes in the process
What is the minimum energy of photon needed for pair production?
hf min = 2E0 (Two times the rest energy of the particle)
How did Carl Anderson discover the positron?
He was using a cloud chamber to observe and photograph trails produced by cosmic rays. He tested if the particles could could pass through a end plate in the chamber.
When a magnetic field is applied to the chamber he knew that the trail of a charged particle would bend in the field. He knew that a positive particle would be deflected by the magnetic field in the opposite direction to a negative particle travelling in the same direction. The slower the particle moved the more it would bend.
When the particle entered the cloud chamber he expected the particle to slow down and bend more afterwards. This was observed however it bent in the opposite direction to which he had expected - he had discovered the positron
The electromagnetic force between two particles is due to ________
Virtual Photons
Why are virtual photons described ass virtual?
Because we cant detect them directly, if we intercept them eg with a detector then we stop them acting.
What is the weak nuclear force responsible for?
Changing protons to neutrons in Beta+ decay and changing neutrons to protons in Beta- decay
What is the W-boson?
The W boson is a force carrier and has a non zero mass and a very short range of non more than 0.001 fm. They have a charge W+ or W- bosons. They change protons into neutrons and vice versa by changing their quark composition. They are responsible for the weak nuclear force.
What is the Feynman diagram. For beta - decay?
Insert
What is the Feynman diagram for beta + decay?
Insert
What is electron capture?
Electron capture is when a proton in a proton rich nucleus turns into a neutron as a result of interacting through the weak nuclear interaction with an inner-shell electron from outside the nucleus. Also known as K capture
What is the Feynman diagram for Electron capture?
Insert
