ELECTROMAGNETIC SPECTRUM
BIOMEDICAL ENGINEERING2006200401 TAE_EUI, KIM
Electromagnetic SpectrumElectromagnetic Spectrum
① Audio freq.② Radio freq.③ Microwave④ Infrared⑤ Visible light⑥ Ultraviolet⑦ X-ray⑧ R-ray
①① Audio frequencyAudio frequency
20~20,000Hz ; long wave length
No change with respect to area or position Because it’s too low freq. long wave length to neglect
cf
8
73 10
30 1 10130
msHz m
Hzs
10,000km( diameter of the earth)
Independent on positionECG bit overlapped, similar to the range of EMG.EEG is lower than 20Hz No sound from speaker
②② Radio frequencyRadio frequency
1) Low freq. :30kHz ~ 300kHz (10km ~ 1km)
2) Medium freq.:300kHz ~ 3MHz (1km ~ 100m)
3) High freq.:3MHz ~ 30MHz
(100m ~ 10m)
②② Radio frequencyRadio frequency
7( ) 10sin(2 3 10 )s tV t 78
10 1:3 103 10
mT sms
83 10 mc s
oV
10
101 period delayed
90 delay
7
13 10
s
②② Radio frequencyRadio frequency3) High freq.:3MHz ~
30MHz (100m ~ 10m)
Able to describe magnitude of each wave at the same time. WAVE PROPAGATION
In high frequency range, as circuits get bigger, we cannot say it is a same signal.Possible to adjust Circuit Analysis within 1M (Low freq.)whereas not to adjust Circuit Analysis over 1M (High freq.)
Differentiate by means of time
The length of antenna should be longer than half of wave length.The reason to try to use high Freq.Antenna can be shorter.
②② Radio frequencyRadio frequency
4) Very High freq. (VHF) : 30MHz ~ 300MHz (10m ~ 1m)
Ex) TV
5) Ultra High freq. (UHF) : 300MHz ~ 3GHz (1m ~ 0.1m)Ex) Mobile
③③ MicrowaveMicrowave
1) Centimeter Wave : 3GHz ~ 30GHz (10cm ~ 1cm)
;Heavily Comm.Ex) Satellite
2) Millimeter Wave : 30GHz ~ 300GHz (10mm ~ 1mm)
;High comm.
3) Sub-millimeter Wave : 300GHz ~ 3THz ( 1mm ~ 0.1mm
);Not so much
④④ InfraredInfrared
1) Far infrared :
2) (Intermediate)Infrared :
4 510 ~10m m
10 ~1m m
⑤⑤ Visible lightVisible light
Red (Longest )
Violet (Shorter )
Reflect our body
⑥⑥ UltravioletUltraviolet
⑦⑦ X - rayX - ray
⑧⑧ R - rayR - ray
cE hv h
Penetrate through our bodyPlank constant
Energy
In summaryIn summary
1 2: hundreds nm (Visible light) : tens um (Infrared light)
1T
Things emit electromagnetic
4tW T
2898m m
T
3000 10300
mTemp. of hands :
Radiation ThermometerRadiation Thermometer
Shutter Lens IR Sensor
Pyroelectric Sensor
Thermometer
Radiation Thermometer
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