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-RESEARCH BASIC ELECTRONIC COMMUNICATIONS SYSTEM
Did you know that electromagnetic waves can not only be
described by their
wavelength, but also by their energy and frequency? All three of
these things
are related to each other mathematically. This means that it is
correct to talk about
the energy of an X-ray or the wavelength of a microwave or the
frequency of a radiowave. The electromagnetic spectrum includes,
from longest wavelength to shortest:
radio waves, microwaves, infrared, optical, ultraviolet, X-rays,
and gamma-rays.
Wavelength Frequency
ULF 100,000 km to 10,000 km 3 - 30 Hz
ELF 10,000 km to 1,000 km 30 to 300 Hz
VF 1,000 km to 100 km 300 Hz to 3 kHz
VLF 100 km to 10 km 3-30 kHz
LF 10 km to 1 km 30-300 kHz
MF 1 km to 100 Meters 300 - 3000 kHz
HF 100 to 10 Meters 3 - 30 MHz
VHF 10 to 1 Meter 30 - 300 MHz
UHF 1 Meter to 10 cm 300 MHz - 3 GHz
SHF 10 cm to 1 cm 3 - 30 GHz
EHF 1 cm to 100 mm 30 -300 GHz
ELF WAVES Frequency is 60 Hz, as their sources are any
alternatingcurrent, especially strong near high voltage
transmissionlines .
RADIOWAVES
AM frequency given by stations: 550 1600 kHz (= 1.6 MHz)FM
frequency given by stations: 88 108 MHzAM = amplitude modulated ,
FM = frequency modulated
TV WAVESTV stations use higher Fr waves to get better resolution
=reception. 54 806 MHz , many channels
http://science.hq.nasa.gov/kids/imagers/ems/waves4.htmlhttp://science.hq.nasa.gov/kids/imagers/ems/waves4.html
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MICROWAVES
CELLULAR PHONE WAVES: frequency 880 MHz =0.88 GHz ,'cell ' is
the area covered by the antenna of( receiving orsending) company -
therefore 'hand-off'.
MICROWAVE OVEN heat water ( in food ) ; 2.45 GHz =
2,450MHzRADAR: used ( in conjunction with the Doppler Effect )
inspeed traps by police, in missiles to find airplanes, tanks,etc.;
used by airports to guide airplanes, most 1 100 GHz( G = giga )
INFRAREDJust below visible red, also called heat radiation .
With specialcameras used to find heat losses from houses; by army
todetect heat radiation from engines, people.
VISIBLELIGHT
RED, YELLOW, GREEN, BLUE, VIOLET - no white or black !!!White is
the sensation for our brain when primary colors ( red,blue and
green) fall onto the retina at the same time . Blackis the absence
of any light .
ULTRAVIOLET
ALPHA- UV is energetic enough to cuase chemical reactionBETA UV
causes damage to cell structure (tanning) and cancause genetic
damage to cell DNA => possible cancer .
X-RAYS
SOFT - X rays = lower Fr range; used for taking
x-raypictures.HARD - X - rays = higher Fr range; used in
cancertreatments to kill cancer cells.
GAMMARAYS
Frequency range overlaps with hard X-rays. Gamma raysoriginate
though in the nucleus of atoms, not by electron
jumps between energy levels as frequencies higher thaninfraded
do .
