Chapter 1 Flashcards
Proton and neutron mass (kg)
1.67x10-27 kg
Proton and Electron Charge (Coulomb)
+1.60x10-19 (proton)
-1.60x10-19 (electrons)
Electron mass (kg)
9.11x10-31 kg
Definition of an isotope?
Atoms with the same number of protons and different number of neutrons (also called nuclides)
What is specific charge and what is its equation?
It is a characteristic property of a nucleus
Specific charge =Charge (c) / mass (kg)
What does the strong nuclear force do?
It overcomes electrostatic repulsion and holds nucleons together
Range of the strong nuclear force
Very short range (about 3-4 fm (femtometers, 10^-15) down to about 0.5 fm where it becomes repulsive to stop protons and neutrons contracting.
Alpha decay
A A-4 `` 4
X –> y + He
Z Z-2 2
Beta minus decay
A A 0
X –> y + B + antielectron neutrino
Z Z+1 -1
Betus plus decay
A A 0
X –> y + B + electron neutrino
Z Z-1 +1
Gamma decay
A A 0
X –> y + gamma
Z Z 0
What is a photon?
The electromagnetic waves emitted when charges particles lose energy (discrete amount)
How can charged particles lose energy? (2 ways)
Slowing down/ changing direction
Moving to a lower energy level
Photon energy equation
E=hf
E=hC/ wavelength
What is the planck constant (h)?
h= 6.63x10^-34 Js
What speed does a wave travel at (C) ?
the speed of light, C= 3x10^8
What is an antiparticle?
Has the same rest mass as its opposing particle but has the opposite charge.
What happens when a particle and a antiparticle meet?
They annihilate each other, converting all mass to energy in the form of a pair of photons.
What is the minimum photon dictated by?
It is dictated by the rest energies of the annihilating particles
– 2E = 2hf(min) (2 particles create two photons moving in opposite directions)
What is annihilating used in?
It is used in P.E.T scanners where positron emitting tracers are injected into a person, when the positrons meet electrons they annihilate and the produced gamma photons can be detected outside the body.
What is pair production?
When a single photon spontaneously produces a particle/antiparticle pair.
- Particle/anti conserves charge
- the opposite direction conserves momentum
- Min photon energy: hf(min)=2E (rest energy of each particle)
What do we measure particle energy in?
electron volts
1eV = 1.6x10^-19 J
What is 1MeV in J?
MeV = 1.6x10^-19 J
What is the rest energy of an electron/positron?
0.551 MeV
What exchange particle causes the strong nuclear force (like charges repelling)?
Virtual photon
What force causes beta decay and what is the exchange particle?
Weak nuclear force
W boson
Difference between photons and W bosons
W bosons: have a rest mass
have a very short range (~0.001fm)
are charged
Other weak nuclear force interactions
- Neutron interacting with a neutrino,
changes into a proton and beta minus
particle - Proton interacting with an antineutrino,
changes into neutron and beta plus
particle
Electron capture mechanism
A proton interacting with an electron changing into a neutron and neutrino (W+ Boson)
What does a force carrier do?
They are exchanged when the electromagnetic force and the weak nuclear force act.
3 example of force carriers
Gamma photons
W Bosons
The pion
What interaction is the pion responsible for?
The strong nuclear force.
