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Unformatted text preview: NNSE 508 EM
Home assignment # 3 Due: February 15, 2011 1. For a normal incidence of plane monochromatic EM wave from a medium with
impedance 1 to a medium with impedance 2,
a) write the wave phasors (electric and magnetic fields) for incident, transmitted and
reflected waves. Note: pay specific attention to relationships between signs that can be
obtained from Maxwell equations.
b) Applying boundary conditions show that reflection and transmission coefficients are as
follows: r Er 2 1 Ei 2 1 t Et
22 1 r
Ei 2 1 2. Electromagnetic radiation loses intensity when it reflects from surfaces with roughness
greater than the wavelength . Assuming you would like to use the lowest energy source
possible, determine the frequencies of EM waves which would be appropriate to
characterize
(a) cars on a road
(b) the presence of mountains
(c) micronsize voids in insulators
(d) atomic steps on a single crystal
and identify the types of EM waves present in each case (e.g. cosmic
waves, UV, visible, etc.)
2K
2
1 coska , where a is the lattice
4. The dispersion relationship for lattice vibrations is M
constant, M is the atomic mass, and K is an effective interatomic interaction (spring) constant. Sketch
the dispersion relationship and derive an expression for the group velocity.
5. Show that at low frequencies (f < 1013 Hz) the reflectivity and conductivity of metals
f 0 . Confirm that at these frequencies metals can be treated as “good conductors”. are related by HugenRubens equation: R 1 4 6. Assuming that in alkali metals each atom provides one free electron, find in all alkali
metals:
a) electron density;
b) electron mean free path at 300K;
c) scattering time
Given:
Metal
Li
Na
K
Rb
Cs
Density, g/cm3
0.525
0.961
0.850
1.52
1.89
8.6
4.2
6.15
12.5
20
Specific resistivity cm ...
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 Spring '11
 SergeOktyabrsky

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