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Unformatted text preview: EAD 234B: E&M Homework #2 Due Thursday, April 15, 2010 (1) Assume that the ionosphere may be modeled as a planestratified plasma (n e ∝ height) with B = 0. Show that the trajectory of an electromagnetic wave packet launched from the ground is a parabola. Note: one can use the same type of calculation to verify a sinusoidal trajectory through a slab light pipe in which n e ~ y 2 for both positive and negative y values. (2) The distance from the Earth to a pulsar can be estimated by observing the dispersion of the radiofrequency pulses as they cross the interstellar medium. a) Suppose the medium is a plasma of N electrons/cm 3 . What is the index of refraction n( ω ) where ω is the angular frequency of a wave? b) The pulsar emits a short pulse that contains a broad range of frequencies. We observe the pulse in a receiver that is tuned to a narrow band δω about an adjustable central frequency ω . We measure the time difference δ t between the arrival of two components of the pulse, centered at frequencies ω and ω + δω , where δω << ω . This can be done in a single receiver if the pulsar has a precise pulse rate {as is the case. Pulsars are the most accurately periodic macroscopic phenomenon ever observed}. case....
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This note was uploaded on 05/14/2010 for the course EAD 234 taught by Professor Ncl during the Spring '10 term at École Normale Supérieure.
 Spring '10
 NCL

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