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EMR Introduction

EMR Introduction. Lesson One. You will be able to. Describe qualitatively how electromagnetic radiation is produced Identify the various parts of the electromagnetic spectrum Explain how electromagnetic radiation waves are produced and transmitted. James Clerk Maxwell (1865).

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EMR Introduction

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  1. EMR Introduction Lesson One

  2. You will be able to • Describe qualitatively how electromagnetic radiation is produced • Identify the various parts of the electromagnetic spectrum • Explain how electromagnetic radiationwaves are produced and transmitted.

  3. James Clerk Maxwell (1865) • A theoretical physicist that expanded upon the work of Oersted and Faraday.

  4. EM Theory is based upon 4 principles: • A moving charge or current in a wire generates a magnetic field about itself. (Oersted) • A conductor moved through a changing magnetic field generates a current in the conductor (Faraday) • Maxwell theorized that a changing electric field can produce a changing magnetic field • Maxwell postulated that a changing magnetic field could produce a changing electric field.

  5. A Changing Electric Field Produces a Changing Magnetic Field • open switch, E =0 • when switch is closed, charges accumulate on the two plates • E increases from zero to a maximum in some time • Strength of depends upon the rate at which changes

  6. A Changing Magnetic Field Produces a Changing Electric Field • Open switches to electromagnets, = 0. • When the switches are closed, increases from zero to a maximum • When changes, is generated • Strength of

  7. Electromagnetic Wave (EM Wave) or Electromagnetic Radiation (EMR) • consists of a changing electric field which is perpendicular to a changing magnetic field • so an EM wave or EMR is • -an EM wave is generated by the acceleration of a charge or changing magnetic field.

  8. Theory • Calculations lead to a mathematical description of the speed of such waves as being about 3.00 x 108 m/s. • Since this was the same as the speed of light, Maxwellproposed that light was a form of this electromagnetic radiation.(EMR) • He also predicted that many other forms of this radiation would be discovered • Since his time, an entire spectrum of EMR has been detected. (see page 638)

  9. NOTE: The frequencies or wavelengths must be memorized for each type of EMR. You should also know the approximate wavelengths of the different colors of light.

  10. Electromagnetic Spectrum • A range of values from radio waves to cosmic radiation. • All of these waves behave as light. That is they reflect, refract, interfere and diffract. • Since these were waves, Maxwell believed that they required a medium to travel through. • He invented a medium called the luminiferous ether. Michelson and Morley later proved that the ether did not exist

  11. Heinrich Hertz • Designed an experiment that verified Maxwell’s prediction • See text page 644.

  12. Set Up of Experiment • A spark (an accelerating charge)is produced by the induction coil. • This is a changing electric field which will create a changing magnetic field….in other words an electromagnetic wave. It is detected by the loop receiver.

  13. Assignment: • Read text pages 634-647 • Do Check and Reflect p. 647 #1,2,4,5,7,8,10,11,14

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