This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Princeton University—Physics 501 Problem Set 7 Due: Dec. 6, 2011 1) (J7.4) A plane polarized electromagnetic wave of frequency ω in free space is incident normally on the flat surface of a nonpermeable medium of conductivity σ and dielectric constant . a) Calculate the amplitude and phase of the reflected wave relative to the incident wave for arbitrary σ and . b) Discuss the limiting cases of a very poor and very good conductor, and show that for a good conductor the reflection coefficient (ratio of reflected to incident intensity) is approximately R = 1 2 ω c δ where δ is the skin depth. 2) The Earth’s ionosphere can be approximated by stratified horizontal planes (actually spherical shells) in which the electron density N increases with altitude z up to some maximum N max ’ 10 12 /m 3 , and then decreases. Snell’s Law applied to adjacent planes shows that a shortwave radio beam follows a path such that n ( z )sin θ ( z ) is constant, where n ( z ) is the refractive index as a function of height and θ is the angle of the beam with respect to the vertical. a) Neglecting the effect of the Earth’s magnetic field, show that a radio wave is reflected at or below the altitude at which the plasma frequency is equal to the...
View
Full Document
 '11
 MARLOW
 Conductivity, Magnetism, Shortwave Radio, plasma frequency, maximum useful frequency, shortwave radio beam, stratified horizontal planes

Click to edit the document details