6.4 - Particles - Nuclear and Particle Physics Flashcards
What are the four fundamental forces
Strong nuclear
Electromagnetic
Weak nuclear
Gravitational
What does strong nuclear force do
It is experienced by nucleons
What does electromagnetic force do
Experienced by static and moving charged particles
What does weak nuclear force do
Responsible for beta decay
What does gravitational force do
Experienced by all particles with mass
What is the mass energy equivalence equation
E = mc^2
What is the most stable isotope
Iron (Fe-56)
What is the correct notation for elements
A = Nucleon number
X = Element
Z = Proton number
What is the range of strong nuclear force
Repulsive up to 0.5fm and attractive up to 3fm
What is an antiparticle
Every particle has a corresponding antiparticle with the same mass but opposite charge
What is the antiparticle for an electron
Positron
What is a hadron
A type of particle which is affected by the strong nuclear force
What are the classes of hadrons
Baryon (3 quarks)
Mesons (2 quarks)
What is an example of baryons
Protons and neutrons
What are leptons
Fundamental particles which are not subject to strong nuclear force (but do via weak nuclear force)
What are examples of leptons
Electrons and neutrinos
What are the types of quarks
Up (u)
Down (d)
Strange (s)
and all have anti particles
What are the charges of up down and strange
Up = +2/3e
Down = -1/3e
Strange = -1/3e
What is the quark composition for protons and neutrons
Proton (uud)
Neutron (udd)
Which quark decays in beta minus decay
A down quark turns into an up quark
What is the activity of a source
The number of radioactive decays per second (measured in Becquerels, Bq)
What is the Activity equation
A = λN
A = Activity
λ = Decay constant
N = number of radioactive nuclei
What is the half life of an isotope
The average time taken for the activity of a sample to halve
What is the equation with activity of a sample
A = Aoe^–λt
What happens when a particle and antiparticle meet
Annihilation
Which releases 2 gamma rays
2 waves are released in order to conserve momentum
Mass of the particles will transform into the energy equivalent
What is mass defect
The difference between the total mass of all the nucleons separately compared to the mass of nucleus
What is binding energy
The energy required to separate a nucleus into its parts
What is nuclear fission
Where an unstable nucleus splits into 2 smaller nuclei
The binding energy per nucleon increases when fission occurs therefore the overall process releases energy
What is fusion
When 2 small nuclei fuse together to create a larger nuclei
The new nucleus has a larger binding energy per nucleon than the old nuclei therefore energy is released in this process
Does fusion or fission release more energy
Fusion releases a lot more
Why is it difficult for fusion to occur on earth
The repulsive force between the 2 positive need to be overcame so heat is created and there is no material which can withstand it and be cost effective
How is fission used in reactors
Rods of uranium absorb neutrons and become unstable and then split into 2 daughter nuclei releasing 2 or 3 more neutrons then go on to be reabsorbed by another uranium-235
What is the purpose of a moderator (water)
Slow down the neutrons so they travel slow enough to be absorbed
They do this through elastic collisions
Why are control rods useful
They stop the chain reaction from being out of control
They absorb neutrons so that only 1 of the neutrons released in each reaction can go on to be absorbed by another uranium
If not the reactor would overheat
What is a chain reaction
When 1 neutron from each decays goes on to cause another decay so the amount of energy remains constant
How is nuclear waste (used fuel rods) disposed of
First stored in cooling ponds
Then put in a sealed container and stored deep underground or underwater
What is an environmental benefit and risk of nuclear power
Benefit - No release of greenhouse has, no fossil fuels consumed
Risk - leak or escape of material can be catastrophic
