6.007 Lecture 29: Reflection and Transmission of EM Waves
Reflection & Transmission of EM Waves
Reading – Shen and Kong – Ch. 4
Outline
• Everyday Reflection • Reflection & Transmission (Normal Incidence) • Reflected & Transmitted Power • Optical Materials, Perfect Conductors, Metals
1 TRUE or FALSE
1. Destructive interference occurs when two waves are offset by a phase of ½πm, or half a wavelength.
2. The intensity of a plane wave oscillates in time. This means it is always constructively and destructively interfering with itself. Coherent light Propagation 3. In a double-slit direction experiment, as Barrier with you decrease the double slits space between the slits, the interference destructive constructive peaks decrease interference interference proportionally. detector screen
2 Waves in Materials ω k = (n − jκ ) c
Index of refraction
Absorption coefficient 2κω 4πκ α = = c λ
3 Incident and Transmitted Waves same amplitudes E Normal Incidence H incident wave
transmitted wave reflected wave
Medium 1 Medium 2 Incident Wave Transmitted Wave
4 EM Wave Reflection Metal Reflection Thin Film Interference
Dielectric Reflection Metal Reflection © Kyle Hounsell. All rights reserved. This content Image in the Public Domain is excluded from our Creative Commons license. For more information, see Image by Ali Smiles :) http://ocw.mit.edu/fairuse. http:/www.flickr.com/photos/ 77682540@N00/2789338547/ on flickr
Cell Phone Reflection AM Radio Reflection
5 IncidentE and Transmitted Waves incident wave H Normal Incidence
transmitted wave reflected wave
Medium 1 Medium 2
Incident Wave Known Transmitted Wave
Define reflection Reflected Wave coefficient as
Define transmission coefficient as
6 Key Takeaways
• Define the reflection coefficient as
• Define the transmission coefficient as
2
7 E-Field Boundary Conditions
area A nˆ EA⊥ + + + + +δ + ρs surface EB⊥ Normal is discontinuous at a surface charge.
C EA nˆ δ surface EB L Tangential is continuous at a surface.
Known
8 H-Field Boundary Conditions
area A nˆ μoHA⊥ δ surface μoHB⊥ Normal is continuous at a surface.
C nˆ HA K δ HB Tangential is discontinuous at L a surface current .
9 Incident EM Waves at Boundaries
E incident wave H Normal Incidence
Medium 1 Medium 2
Incident Wave Known