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23 Electromagnetic Waves

23 Electromagnetic Waves. Principle. Faraday’s law: time-varying B -field creates E -field ( emf ) Maxwell: time-varying E -field generates B -field ( emf ). James C Maxwell British Scientist (1831 – 1879). EM waves were PREDICTED by J.C. Maxwell in 1865. Light is part of the EM wave

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23 Electromagnetic Waves

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  1. 23Electromagnetic Waves

  2. Principle Faraday’s law: time-varying B-field creates E-field (emf) Maxwell: time-varying E-field generates B-field (emf) James C Maxwell British Scientist (1831 – 1879) EM waves were PREDICTED by J.C. Maxwell in 1865. Light is part of the EM wave Heitz first detected the EM waves in 1887 after Maxwell died (1879). Another great prediction(s) was made by Einstein from his General Relativity. Heinrich R Hertz German physicist (1857 –1894)

  3. Properties of EM Waves • Transverse Wave; Both E & B perpendicular to propagation, k. E, B and k follow the right-hand rule • EM waves can be created and travel in vacuum (no medium required) with unchanging speed c • E & B are in phase and E= cB • (in vacuum) v = lf

  4. EM Spectrum

  5. Images Taken in Different EM Wave Regions

  6. Sinusoidal Waves

  7. Energy in EM Waves S: energy per unit area per unit time or power per unit area and the average value, Sav called intensity, I.

  8. Radiation Pressure

  9. Nature of Light: Wave-Particle Duality

  10. Wave Fronts Geometric optics & Physical Optics Rays & Waves

  11. Reflection & Refraction

  12. Index of Refraction & Snell’s Law Normal Incident qa qr Reflection na nb Angles respect to normal line All the rays in same plane Refraction qb

  13. Experience: Driving & Reflections

  14. Value of Refractive Index Air 1.0003

  15. Total Internal Reflection Critical angle: when qb = 90o, qa = qc = sin-1(na/nb) 90 qc

  16. Dispersion: n= n(l)

  17. Polarization Linear polarization Circular polarization (left)

  18. Mirage, Blue Sky, & Traffic Lights

  19. Summary: EM Waves, Speed & Spectrum

  20. Sinusoidal Waves and Energy

  21. Nature of Light

  22. Reflection & Refraction Total Internal Reflection:

  23. Reflection & Refraction: Animations Animation of Refraction (rays) Animation of Refraction (waves)

  24. Dispersion

  25. Polarization

  26. Homework

  27. Test III Score Distribution Your grade =points/16x100% Number of Students Correct Points

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