Monday, May 19, 2008

Last class day before IB exam.

Handed out summary.
Went over radioactive decay - types of decay (alpha, beta, gamma)
Described the rules for writing decay equations.

Briefly describes classes of particles (leptons (light), hadrons (heavy), gauge bosons (interactions)). In equations, lepton number is conserved as is baryon number.

Hadrons consist of mesons and baryons (particles like proton and neutron)
Leptons include the electron and neutrinos.
Gauge bosons include the photon.

To conserve lepton number, in the decay of a neutron into a proton and electron, you must also have an anti-neutrino.

Went over several decay equations showing that nucleon number, charge number, baryon number and lepton numbers must be the same on both sides of the equation.

Problems in radioactive decay:
Two ways of looking at decay: delta N/delta t = - lambda * N
lamba is the decay constant = decay rate/number of remaining particles

A = Ao * (1/2)^(t/T 1/2)
T 1/2 is the half life
A is the amount remaining
Ao = original amount

The relation between the two ways of looking at decay is: lambda = ln 2/halflife

Students did several problems on radioactive decay.

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Went over photon energies when an electron changes energy levels. Calculated energies of photons, wavelengths, and frequencies.

Showed table of quantum numbers:

n = principal quantum number n = 1,2,3,4...
l = orbital quantum number. For a given n, l = 0, 1, 2, n-1
ml = magnetic quantum number. For a given n and l, ml = l, l-1, ...0, -1, -2, -l
ms = spin quantum number. For the electron, ms = 1/2, -1/2

Also handed out summary packets for astrophysics option.