# Module 3d - 3/2/2009 Module 3 Lecture 4 Reflection and...

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3/2/2009 1 Page 1 Module 3 Lecture 4 Reflection and transmission of EM waves Page 2 On the program today • What happens to a uniform plane wave incident on an interface between two media (one of which can be vacuum)? E and H Field Reflection and Transmission coefficients • ESSENTIALLY SECTION 10.8 FROM SADIKU

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3/2/2009 2 Page 3 A couple of useful concepts Beer’s law: (its not what you think!) – Empirical law which states that light propagating through materials attenuates exponentially with distance. – Maxwell’s theory predicts that for waves in materials with s or e ” ≠ 0, the propagation constant includes an attenuation constant a, hence fields decay exponentially Transverse Electro-Magnetic waves: TEM – A designation for waves in which all E and H field vectors are located in the plane PERPENDICULAR or “Transverse” to the direction of propagation Page 4 First let’s recall the expressions for forward and backward E and H waves ±z
3/2/2009 3 Page 5 E and H are related not only in magnitude but also in orientation P P 1 ss    H a E E a H where a p is in the direction of EH Page 6 Useful formulas in lossless, charge-free media   22 0 j j j j j  e  e 1 p u e  , and in nonmagnetic media ( r = 1), p r c u e   0 , ro r o r o r j j  e e where intrinsic impedance of free space is   7 9 4 x 10 / 10 / 36 120 o o o o Hm or Fm 

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3/2/2009 4 Page 7 Reflection and transmission of plane waves on a plane interface between two media Page 8 Boundary conditions Tangential components of E and H fields are continuous across boundaries, unless there is a surface current and then H t is discontinuous
3/2/2009 5 Page 9 Write down generic expression for all fields in the two regions (either side of interface) Consider   1 1x ( , ) cos z ii o z t E e t z a   Ea incident fields 1 1 1 1 xy 1 and i z j z z j z i i i o s o s E E e e e e  E a H a reflected fields 1 1 1 1 1 and r z

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## This note was uploaded on 09/27/2011 for the course ENGINEERIN 3600 taught by Professor Victor during the Spring '11 term at Carleton CA.

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Module 3d - 3/2/2009 Module 3 Lecture 4 Reflection and...

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