Electromagnetic Waves

"Basic research is what I am doing when I don't know what I am doing"
Wernher von Braun

• At the end of the nineteenth century James Clerk Maxwell was responsible for bringing together the work of Coulomb, Ampere, Faraday and others, to provide an elegant theoretical description of electricity and magnetism.  Classical electromagnetism was described  by four "simple" equations known as Maxwell's equations .  These equations provided the "explanation" for electromagnetic waves.
  
  
• An electromagnetic wave is a transverse wave comprised of oscillating Electric and Magnetic fields.  Mathematically the analysis of EM waves is rather complex.  A plane polarised electromagnetic wave traveling from left to right can be represented as indicated below.


The "traveling nature of the wave is represented thus, where E represents the electric field and H the magnetic field.


• Visible light is a very small part of the electromagnetic spectrum.  The full EM spectrum extends continuously from the very low frequency E and B oscillations of radio waves through microwaves, infra-red, visible light, ultra-violet, X-rays  to very high frequency gamma rays.
  
  
  


• The speed of electromagnetic waves (of all frequencies and wavelengths) in a vacuum is equal to the speed of light, c = 3 x 10⁸  m/s.  Speed, frequency (f) and wavelength () are related by the usual relationship
  
  
  
•  Using Maxwell's equations it can be shown that the speed of light is given by
  

• Using Maxwell's decription of electromagnetic waves it is possible to explain many of the properties of the interactions of visible light with matter.  The details of such explanations are technically quite difficult  and are typically covered in senior level Physics courses.  In the following discussion we will investigate some of the consequences of these properites, for example, the law of reflection, law of refraction (Snell's law), total internal reflection, dispersion, interference and diffraction.

• The electromagnetic spectrum NASA video.

• Maxwell brief biography video.
  

• Maxwell's equations and electromagnetic waves video.
  

"I've heard that the government wants to put a tax on the mathematically ignorant. Funny, I thought that's what the lottery was!"
Gallagher

 

Dr. C. L. Davis
Physics Department
University of Louisville
email: c.l.davis@louisville.edu