Exam flashcards
(27 cards)
What is the time averaging of a plane wave?
1/2
What is the assumption for the thin lense equation?
Radius of curvature is much larger than thickness of lens
How do we obtain the magnifcation?
Comes from α/θ
d=f2α=f1θ
What is the assumption for the equipartition theorem?
In the classical limit
What is the energy for SHO in high temperature limit?
kBT
What is the assumption for the Fermi energy?
T ~ 0
What is the distribution function when calculating the energy?
f(E) = 1 for E < EF
and = 0 for E > EF
What is the physical meaning of the distribution function?
The mean occupation of a single particle state in the system
What is the chemical potential for phonons?
0
They can be freely created and absorbed
What is the limit for ex as x goes to 0?
ex goes to 1+x
How do we find the Fermi energy?
Find N by integrating from 0 to EF
What is the principle of superposition for the electric field?
The total electric field will be the sum of the static field plus the field of the wave
What is the justification of Fermat’s principle?
Each part of a wavefront acts as a source of secondary waves whose envelope forms the next wavefront (Huygens’ principle). For the path where the overall phase is extremised, small perturbations to the path do not change the phase so these add constructively. Elsewhere, the paths cancel out.
What is the differential of cosh(ax)?
asinh(ax)
What is the differential of sinh(ax)?
acosh(ax)
What are the limits of cosh and sinh?
As x goes to 0 cosh goes to 1 and sinh goes to 0
What are examples of fermions?
Protons, neutrons, electrons
What are examples of bosons?
Phonons, photons, higgs
What are the contributions to the heat capacity for a ferromagnetic material?
Conduction electrons
Debye term
Magnons
When is H not a function of B?
Ferromagnetic material
Due to hysteresis
By what factor does amplitude decay in a material?
1/e in the skin depth
What are the types of phonons?
Acoustic, move in phase
Optical, move in opposite directions
What do the types of phonons represent?
Acoustic, Debye model
Optical, Einstein model
What does isotropic mean?
The behaviour of the system response is parallel to applied field
for all directions of the applied field
