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ELECTROMAGNETICS
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WAVELENGTH
| c = speed of light 2.998 × 108 m/s |
| l= wavelength [m] |
| c=lf | f = frequency [Hz] |
| c=E / B | E = electric field [N/C] |
| B = magnetic field [T] |
| 1Å = 10-10m | Å= (angstrom) unit of wavelength equal to 10-10 m |
| m = (meters) |
WAVELENGTH SPECTRUM
| BAND | METERS | ANGSTROMS |
| Longwave radio | 1 - 100 km | 1013 - 1015 |
| Standard Broadcast | 100 - 1000 m | 1012 - 1013 |
| Shortwave radio | 10 - 100 m | 1011 - 1012 |
| TV, FM | 0.1 - 10 m | 109 - 1011 |
| Microwave | 1 - 100 mm | 107 - 109 |
| Infrared light | 0.8 - 1000 mm | 8000 – 107 |
| Visible light | 360 - 690 nm | 3600 - 6900 |
| violet | 360 nm | 3600 |
| blue | 430 nm | 4300 |
| green | 490 nm | 4900 |
| yellow | 560 nm | 5600 |
| orange | 600 nm | 6000 |
| red | 690 nm | 6900 |
| Ultraviolet light | 10 - 390 nm | 100 - 3900 |
| X-rays | 5 - 10,000 pm | 0.05 - 100 |
| Gamma rays | 100 - 5000 fm | 0.001 - 0.05 |
| Cosmic rays | < 100 fm | < 0.001 |
1 Intensity of Electromagnetic Radiation [watts/m2]:
I=Ps /4pr2
I = intensity [w/m2]
Ps = power of source [watts]
r = distance [m]
4pr2 = surface area of sphere
2 Force and Radiation Pressure on an object:
(a) if the light is totally absorbed:
F=(IA/c) , Pr = (I/c)
F = force [N]
I = intensity [w/m2]
A = area [m2]
Pr = radiation pressure [N/m2]
c = 2.99792 × 108 [m/s]
(b) if the light is totally reflected back along the path:
F=(2IA / c) , Pr = (2I/c)
3 Poynting Vector [watts/m2]:
cB = E
m0 = the permeability of free
space 4p×10-7 T·m/A
E = electric field [N/C or V/M]
B = magnetic field [T]
c = 2.99792 × 108 [m/s]
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