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Electromagnetic Waves

Electromagnetic Waves. Maxwell’s Equations Plane waves Polarization. Electromagnetic Waves. Chapter 34 Read Sections 1, 5, 6, 7, 8 Read Sections 3, 4 lightly Don’t read section 2. Reading Questions. Maxwell’s equations are a set of how many equations?. 1. Two 2. Three 3. Four 4. Five

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Electromagnetic Waves

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  1. Electromagnetic Waves Maxwell’s Equations Plane waves Polarization

  2. Electromagnetic Waves Chapter 34 Read Sections 1, 5, 6, 7, 8 Read Sections 3, 4 lightly Don’t read section 2

  3. Reading Questions Maxwell’s equations are a set of how many equations? 1. Two 2. Three 3. Four 4. Five 5. Six

  4. Reading Questions Maxwell’s equations are a set of how many equations? 1. Two 2. Three 3. Four 4. Five 5. Six

  5. Reading Questions Experimenter A creates a magnetic field in the laboratory. Experimenter B moves relative to A. Experimenter B sees 1. just the same magnetic field. 2. a magnetic field of different strength. 3. a magnetic field pointing the opposite direction. 4. just an electric field. 5. both a magnetic and an electric field.

  6. Electromagnetic Waves • For the past five or six weeks we have been studying Electrostatics and Magnetostatics. We were able to study electrostatics without worrying about magnetism. They both were independent of the other. As you will recall the theory is called Electromagnetic Theory. Thus, the two must be related or interconnected. We got a feel for this when we studied electromagnetic induction. There we saw that a changing magnetic field could create an electric field. Now we will find out that the reverse is also true. A changing electric field creates a magnetic field.

  7. Electromagnetic Waves relativity Does Bill measure a magnetic field? Does Sharon measure a magnetic field?

  8. Reading Questions Experimenter A creates a magnetic field in the laboratory. Experimenter B moves relative to A. Experimenter B sees 1. just the same magnetic field. 2. a magnetic field of different strength. 3. a magnetic field pointing the opposite direction. 4. just an electric field. 5. both a magnetic and an electric field.

  9. Reading Questions Experimenter A creates a magnetic field in the laboratory. Experimenter B moves relative to A. Experimenter B sees 1. just the same magnetic field. 2. a magnetic field of different strength. 3. a magnetic field pointing the opposite direction. 4. just an electric field. 5. both a magnetic and an electric field.

  10. Recall Electromagnetic Waves • Maxwell’s Equations so far

  11. Electromagnetic Waves • Displacement Current

  12. Electromagnetic Waves • Displacement Current

  13. Electromagnetic Waves • Displacement Current

  14. Electromagnetic Waves • Displacement Current

  15. Electromagnetic Waves • Maxwell’s Equations

  16. Electromagnetic Waves • Maxwell’s Equations in free space

  17. Student Workbook

  18. Student Workbook

  19. Student Workbook

  20. Electromagnetic Waves Properties of Electromagnetic Waves • What is the relationship Maxwell found for the speed of electromagnetic waves? • What is the ratio of the electric field to the magnetic field?

  21. Electromagnetic Waves Properties of Electromagnetic Waves • Below is a drawing of a plane electromagnetic wave. Discuss this in your group and make sure everyone understands the figure.

  22. Electromagnetic Waves Properties of Electromagnetic Wave • What is the average energy for an electromagnetic wave? • What is the average power for an electromagnetic wave? • Does an electromagnetic wave have momentum?

  23. Electromagnetic Waves • Electromagnetic Spectrum

  24. Electromagnetic Waves • Pictures of different types of radiation

  25. Electromagnetic Waves • Pictures of different types of radiation

  26. Electromagnetic Waves • Mark the following on the figure. 1. My favorite radio station KISS 108 MHz (Not really, it is WCRB 105.9). What is the wavelength? 2. Where is the color red? What is the wavelength and frequency? 3. My dentists uses X-rays (0.8 nm) to check my teeth. What is the frequency? 4. When I was at MIT I used X band (9 GHz) microwaves to study superconductivity. What is the wavelength?

  27. Student Workbook

  28. Student Workbook

  29. Student Workbook

  30. Class Questions An electromagnetic wave is traveling in the positive y-direction. The electric field at one instant of time is shown at one position. The magnetic field at this position points 1. In the positive x-direction. 2. In the negative x-direction. 3. In the positive y-direction. 4. In the negative y-direction. 5. Away from the origin.

  31. Class Questions An electromagnetic wave is traveling in the positive y-direction. The electric field at one instant of time is shown at one position. The magnetic field at this position points 1. In the positive x-direction. 2. In the negative x-direction. 3. In the positive y-direction. 4. In the negative y-direction. 5. Away from the origin.

  32. Electromagnetic Waves • Radiation Source

  33. Electromagnetic Waves • Radiation Source

  34. Electromagnetic Waves • Polarization

  35. Electromagnetic Waves • Polarization

  36. Electromagnetic Waves • Polarization

  37. Electromagnetic Waves • Polarization – Two Examples Mechanical stress Digital displays

  38. Student Workbook

  39. Student Workbook

  40. Student Workbook

  41. Class Questions Unpolarized light of equal intensity is incident on four pairs of polarizing filters. Rank in order, from largest to smallest, the intensities Ia to Id transmitted through the second polarizer of each pair. 1. Ia = Id > Ib = Ic 2. Ib = Ic > Ia = Id 3. Ib = Ic > Ia > Id 4. Id > Ia > Ib > Ic 5. Id > Ia > Ib = Ic

  42. Class Questions Unpolarized light of equal intensity is incident on four pairs of polarizing filters. Rank in order, from largest to smallest, the intensities Ia to Id transmitted through the second polarizer of each pair. 1. Ia = Id > Ib = Ic 2. Ib = Ic > Ia = Id 3. Ib = Ic > Ia > Id 4. Id > Ia > Ib > Ic 5. Id > Ia > Ib = Ic

  43. Class Questions

  44. Electromagnetic Waves • More pictures

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