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