Particles and Radiation Flashcards
What is the relative charge of a proton?
+1
What is the relative charge of a electron?
-1
Relative charge of a neutron
0
Relative mass of a proton
1
Relative mass of an electron
1/1820
Relative mass of a neutron
1
What letter is used to represent nucleon number?
A
What letter is used to represent proton number?
Z
What is the equation for specific charge?
Specific charge(C/Kg) = charge(C)/mass(Kg)
What are isotopes?
Isotopes are atoms with the same number of protons but a different number of neutrons
How does adding more neutrons affect an atom?
Adding more neutrons makes an atom more unstable. These unstable nuclei may be radioactive and decay to make themselves more stable
What is the range of the strong nuclear force?
< 3fm
When is the strong nuclear force repulsive?
When nucleon separation is less than 0.5fm
When is the strong nuclear force attractive?
When nucleon separation is between 0.5fm - 3fm
What are the forces that act within nuclei?
- Gravitational force
- Strong nuclear force
- Electromagnetic force
What does the electromagnetic force do in nuclei?
It causes the positively charged protons to repel each other
What is the range of the electromagnetic repulsive force?
Infinite
What type of atoms does alpha decay occur for?
Very big atoms with greater than 82 protons
What is an alpha particle?
A particle made up of 2 neutrons and two protons (A helium nucleus)
What is beta minus decay?
The emission of an electron from the nucleus along with an antineutrino particle
What type of atoms does beta minus decay from?
Atoms that are neutron rich (have too many neutrons)
What happens to the nucleons of an atom that undergoes beta minus decay?
- One of the neutrons in the nucleus is changed into a proton
- Proton number increases by one, nucleon number stays the same
Describe how the neutrino was theorised
- Scientist originally thought only an electron was emitted during beta decay
- However observations showed energy of the particles after beta decay was less than before which didn’t fit the principle of energy conservation
- It was then hypothesised that another particle was emitted and it carried away the remaining energy but it had to be neutral, and near zero mass
- This hypothesis was later accepted and this particle was named the neutrino
What is the electromagnetic spectrum?
A continuous spectrum of all the possible frequencies of electromagnetic radiation
What are the traits of an antiparticle compared to corresponding particle?
Same mass and rest energy but opposite charge
Define pair production
- Energy is converted into mass in the form of a particle-antiparticle pair
- Only occurs when there is enough energy to produce the masses of the particles
State the equation for minimum energy needed for pair production
E(min) in MeV = 2Eo where Eo = Rest energy of particle type produced in MeV
Define annihilation
Matter and antimatter meet and mass is converted directly into energy in the form of two gamma ray photons which travel in opposite directions
State the equation for minimum energy needed for annihilation
E(min) in MeV = Eo where Eo = Rest energy of particle type annihilated in MeV
State an application that uses annihilation and describe how it works
- PET scanners work by putting a positron-emitting isotope into the bloodstream, and detecting the gamma rays produced by the electron-positron annihilation occurring
- A scintillator is used to detect gamma rays which are easy to distinguish as these gamma rays are always produced in pairs moving in opposite directions
What are hadrons?
Particles that feel the strong nuclear force
What are the types of hadrons?
Baryons and mesons
What is the most stable baryon which all particles baryons end up decaying to?
The proton
State the baryon numbers of baryons, antibaryons and other particles?
- Baryons = +1
- Antibaryons = -1
- Other particles = 0
What is neutron decay?
Beta-minus decay caused by the weak interaction where a neutron decays into a proton, an electron and an antineutrino
State 2 characteristics of mesons
- Mesons are all unstable
- Quark and antiquark pair
State 2 types of mesons
Pions and Kaons
Which quark is always in a kaon?
Strange quark