1. Optical properties of a conductor
Why do metals reflect so well?
Modification for conductor: A
For bound charges, the spring limits the displacement r
What limits r for free charges?

2. displacement r for bound, unbound charges

3. Optical properties of a conductor
First, start with (opposite case!) of dielectric: (insulator) A
Modification for conductor:

4. Typical plasma frequencies
density N (m-3)
(Hz)
metals
1028
1016
semicond. (pure)
1024
1014
semicond. (doped), fusion expts
1020
1012
ionosphere
(60 to 450 km)
1011
107
interplanetary space
105

5. Optical properties of a conductor
Case of very little damping g<<w: A
For w< wp , check the sign of
Which must be nonzero? n
b) k

6. Optical properties of a conductor
Since wo 0, can we simply shift n(w), k (w)?

7. n,k for metal. Plasma frequency divides two regimes
g=wp/10
g=0
n, k
g=wp/10
n, k A
Which frequencies are transmitted well?
Which are reflected well?

8. Reflectance vs. Wavelength
Plasma frequency of silver

9. Poynting Vector energy density in a vacuum
Its magnitude is the intensity: Power/area
What equation does this look like?
So S is an energy flow vector: energy/area/time

10. Directions of vectors

11. S, irradiance, intensity
For a plane wave in index n, derive the time average intensity

12. The following are always true (definition and basic MaxEqn for plane wave)
Which vector pair is not guaranteed to be perpendicular?
E, S
E, k
E, B
S, E
B, k

13. Preview:

14. Wave equation P. is a solution to It is also a solution to ____: 1) 2)
eqn 1
eqn 2
both
neither