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Radio Waves and Tunnels
Name: Robin R.
Status: student
Age: 40s
Location: N/A
Country: N/A
Date: 2000-2001
Question:
Why do some radio waves fit through a tunnel and others
do not? Some radio stations stay on through a tunnel and others do not?
Replies:
Robin,
Different radio waves are affected differently by a tunnel due to questions
of resonance.
One question relates to the material of the tunnel. Different molecules
oscillate at different frequencies. If the radio wave frequency equals a
natural frequency of the molecules, the wave is absorbed by the material of
the tunnel. Waves that do not match a natural frequency pass through the
tunnel walls with no problem.
Another question relates to the structure of the entire tunnel, rather than
individual molecules. A wave with a wavelength equal to an exact portion of
the length or width of the tunnel may be affected by the tunnel, while other
wavelengths will not. A wavelength significantly longer than the tunnel
will not even notice the tunnel.
These are the main factors to consider when noticing that different radio
waves are affected differently.
Dr. Ken Mellendorf
Illinois Central College
Assuming the tunnel has not been "wired" with an antenna, the transmission
of electromagnetic radiation depends upon the material through which the
wave is being transmitted, (type and thickness), e.g. steel, concrete,dirt.
The frequency of the wave. Some frequencies are transmitted better than
others. The relative size of the tunnel and the wavelength of the
electromagnetic radiation can also be important. For example, the screen on
the door of a microwave oven does not allow the transmission the the
microwave wavelengths -- that is why it is there -- but allows light, also
electromagnetic radiation of much shorter wavelength to pass unimpeded. You
can see the light inside the oven.
Vince Calder
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Update: June 2012
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