U2 - Particles And Radiation Flashcards
What affects the stability of the isotope and why?
No. of neutrons (ie, the more neutrons, the less stable therefore the strong nuclear force can no longer hold the nucleus together.
How do you find specific charge?
Divide the charge (C) of the object by its mass (kg).
What does the strong nuclear force/ strong interaction do and what is it carried by ?
Holds electrostatically repelling nucleons together.
Carried by gluons.
What does strong nuclear force give rise to, to what, at what distances and why ?
Very short range attraction up to 3fm.
Balanced attraction between the strong nuclear force and electrostatic force at 1.5fm.
Very short range repulsion under 0.5fm.
This is all between individual nucleons.
Above 3fm, the strength of the strong nuclear force drops and the strength of the electrostatic force takes over therefore decreased stability.
Give 4 properties of alpha particles.
Highly ionising due to size.
Low penetration due to size.
Charge of +2.
Amu of approx 4. (Mass)
Why were neutrinos hypothesised?
To account for conservation of energy and momentum during beta decay
What happens on the quark level of beta minus decay? (when a neutron decays into a proton)
A down quark in the nuclide decays into an up quark whilst emitting a W- boson.
The w- boson decays into a beta minus particle (electron) and an anti electron neutrino.
Give 3 properties of gamma rays.?
High frequency, very penetrating and weak ionising ability
What is ionisation energy?
The minimum energy required to remove an electron from its GROUND STATE to form an ion.
What is an electron volt defined as?
The energy of an electron when accelerated through a potential difference of 1 V.
How do particles and their antiparticles differ?
In all their properties (i.e. charge, lepton number, baryon number and strangeness) except for rest mass.
What is annihilation?
When a particle and its antiparticle meet and annihilate converting their mass into energy in the form of two photons.
What is the equation used for annihilation and why?
2hf(min) = 2E^0 where E^0 is the minimum photon energy needed.
What is pair production?
When a photon interacts with an atom and has enough energy to produce a particle and it’s antiparticle. Any surplus energy becomes kinetic energy and the photon has to interact with something as it’s massless.
What is the minimum energy required of a photon to undergo pair production? What happens above this?
The total rest energies on the particles involved. For a particle - antiparticle pair, it would be
hf(min) = 2E^0 and the rest is transferred as kinetic energy.
