Electromagnetic Radiation
So
what you see as light is actually an oscillating electromagnetic wave
traveling
into your eyes at the speed of light. Unlike a mechanical wave, a
light wave is three dimensional, having a magnetic and electric
component, which are always perpendicular to each other, oscillating in
phase and moving in the direction of energy propagation as illustrated
in the diagram below.
Animation of a 2-D
mechanical wave compared with the 3-D light
wave,
E is the electric
field and B is the magnetic field.9
Electromagnetic
radiation is special for a couple of reasons; first is that it needs no
medium for propagation, unlike sound waves or standing waves.
Second is that it possesses both wave like and particle like
characteristics, an attribute we will be discussing shortly.
Different types of electromagnetic radiation are classified via the
wavelength, which is the distance between successive crests or troughs
in a
wave. From long radio waves to ultra compact gamma rays and
everything in between, the range of wavelengths is fairly large, as can
be gathered from the following diagram.
Diagram of the
electromagnetic spectrum.19
Our sun emits all kinds of radiation, but
our eyes only see the visible region of the spectrum, and the various
colors are actually different wavelengths within that narrow
band. But is there any energy associated with all of this?
What happens when light strikes a surface, be it your skin or a piece
of metal? Einstein won the Nobel prize for that answer.
Web Project
by P. D. Wallace
University of Alaska Fairbanks
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