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 radiation waves 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, Maxwell proposed 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