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Terms in this set (62)
Why does the pauli principle favour an equal amount of N and Z
favours stability when N and Z are roughly equal due to cost of bringing in a nuclei. To step bring a proton to an unfilled state, it is energetically more favourbale to fill the neutron state corresponding to that energy level. The energy levels for both particles differ slightly, but are close enough for the rule of thumb N = Z.
Why does the stability curve prefer a higher N than Z
In the atomic nucleus, there are two main forces at work; the strong nucleur foce that binds the atoms together and the electric force caused by the proton charge that seperates them. As the atomic number gets higher, the electric force becomes more and more dominant over the estrong force and more neutrons are needed to keep the nucleus together.
Liquid drop model first term: 14A
Strong force; the term scales with volume and is the force between nuclei
Liquid drop model second term: 13A²/³
Strong force; corrects fact that there are no nuclei outside the surface, it scaels with the surface area of the liquid drop
Liquid drop model third term: 0.55(Z²/A¹/³)
Electrostatic repulsion; of the form q²/r
Liquid drop model fourth term: 19(A-2Z)²/A
Pauli Principle; counts the difference between A and N, this is seen by making use of the constraint A = Z + N. Substituting A we find the difference in protons and neutrons A - 2Z = N - Z
mass number; number of protons and neutrons
atomic number; number of protons
number of neutrons (N = A - Z)
several variants of nucleus for the same charge
u in eV
Most stable isotope
the one with the strongest binding energy per nucleon
occurs when an object is moving away from the observer (stretching the wavelength)
occurs when an object is moving towards the observer (pressing the wavelength)
corresponding quantum characteristic of bosons
stimulated emission (forms basis of laser)
corresponding quantum characteristic of fermions
the Pauli principle; two identical fermions cannot occupy the same quantum state, whilst identical bosons can.
boson or fermion?
photon - boson
proton - fermion
Higgs - boson
quark - fermion
What is a boson
force carrier particles (with an integer spin)
What is a fermion
composite particle (with an odd-half integer --> 1/2)
Pauli exclusion principle
two particles cannot co-exist in the same state at the same location at the same time
Electromagnetic force (lorentz force)
responsible for particle decay
Weak nucleur force
holds the kernels of matter, atomic nuclei, together
Strong nucleur force
the strong nucleur interaction; binds the fundamental particles of matter together to form larger particles. Holds together the quarks that make up protons and neutrons. Part of the strong force also keeps the protons andneutronsof an atom's nucleus together.
p + e --> n + v(neutrino)
Atomic number A does not change
Charge Z goes down by one unit
does the electron associated with B- decay emerge with a fixed energy
no, the electron that emerges comes with an electron neutrino and the released energy is distributed between them. Since the electron neutrino is essentially massless, the maximum energy the electron can have is the total energy released. This is the difference between the isotope masses.
why is the sign of the gravitational potential energy positive
binding energy = - gravitational energy
by moving neutrons closer one gains binding energy
Why are neutrinos so hard to detect
they do not have an electric charge, thus they do not contribute to the electromagnetic force. The gravitational force is so weak considereing their mass. The only way a neutrino can interact is through the weak nucleur force. When a neutrino passes through matter and if it hits something head-on it will create electrically charged particles and those can be detected
What is B+ decay
proton transforms into neutron. Positron and neutrino are emitted.
What is B- decay
There are too many neutrons and is therefore unstable. Neutron transforms into proton. Electron and antineutrino are emitted.
What is alpha decay
Emission of a helium particle. Mass number goes down by 4 and proton number goes down by two.
energy gained by an electron as it is accelerated through an electrostatic potential of 1V
the wavelength of a particle
Wavelength emitted by a particle of matter. Planck's constant divided by momentum of the particle.
if v << c --> p = mv
if not p = ymv
The simplest ruler
The shortening of an object along its direction of motion as its speed approaches the speed of light, as measured by an observer not moving with the object.
The simplest clock
The slowing of a clock as its speed approaches the speed of light as measured by an observer not moving with the clock.
observer moving with a constant speed
energy particle in a box
momentum of a particle in a box
p = hn/2L
CoM vs LAB
In the centre of mass frame we view the particle has an initial momentum of zero. Both mass and momentum are conserved
Plab= y(Pcom - v/c(Ecom/c))
Elab/c= y(Ecom/c - v/c(|Pcom|)
Erel = sqrt(m²c⁴ + |p|²c²)
Etot = Ekin + Erest
the form of energy an object has because of its mass
Max kinetic energy of an electron in the photoelectric effect
energy of a photon
the maximum energy is when the wavelength is at a minimum
momentum of a photon
a photon is considered to be a massless particle, so it doesn't have a rest energy as rest energy is caused by the object's mass. So Etot = sqrt(p²c²). Which means |p| = E/c. Since E = hf=hc/l then |p|=h/l. Associated with deBroglie wavelength
atomic nucleus that contains a number of protons and a number of neutrons that are mutually interchanged in comparison with another nucleus. Thus, nitrogen-15, containing seven protons and eight neutrons, is the mirror nucleus of oxygen-15, comprising eight protons and seven neutrons.
Binding force remains nearly the same
What is color charge and can we detect it?
A hadron can consist of three quarks (baryons), one of each color or two quarks (mesons), one of color and one of anti-color. These combinations are calles white or colorless. Color charge cannot bedetected directly, as all particles we can detect are colorless combinations of quarks.
How many colors can a quark have
A quark can either have a green, blue or red (anti) color charge
Why does the stability curve prefer a slightly higher N than Z?
As the atomic number gets higher, the electric force becomes more and more dominant over the strong force, and more neutrons are needed to keep the nucleus together
What keeps atoms stable?
Bohr's solution; only constructively interfering waves are allowed.
relativistic doppler shift
A set of spectral lines that appear in the visible light region when a hydrogen atom undergoes a transition from energy levels n>2 to n=2.
A set of spectral lines that appear in the UV region when a hydrogen atom undergoes a transition from energy levels n>1 to n=1.
A set of spectral lines that appear in the x-ray region when a hydrogen atom undergoes a transition from energy levels n>3 to n=3.
A set of spectral lines that appear in the infrared region when a hydrogen atom undergoes a transition from energy levels n>4 to n=4.
The bohr atom
a model of the atom that describes electrons circling the nucleus in orbits
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