Electromagnetic waves are created as a result of vibrations produced between an electric field and the magnetic field. The propagation of electromagnetic waves through the vacuum happens at a speed of 3 x 108ms-1 and the propagation of electromagnetic waves through any medium happens at a speed which is less than that of the speed in the vacuum.
1.Wave Number
k = 2π/λ
Where λ is the wavelength of the wave
2. Frequency
The frequency of the wave f = ω/ 2π
Where ω is the angular frequency
3. The speed of the wave
v = λf
4.Maxwell’s Equations
5. Oscillating electric and magnetic field
E = Ex(t) = E0 sin (kz – wt)
E0/B0 = c
C = 1/ c is the speed of light in vacuum
V = 1/ v is the speed of light in the medium
3. Electromagnetic Spectrum
| Type | Wavelength range | Production | Detection |
| Radio | ＞ 0.1 m | Rapid acceleration and deacceleration of electrons in aerials | Receiver aerials |
| Microwave | 0.1 m to 1mm | Klystron value and magnetron value | Point contact diodes |
| Infra-red | 1mm to 700nm | Vibrations of atoms and molecules | Infrared photographic film,Thermopile, Bolometer |
| Light | 700nm to 400 nm | When electrons move from one energy level to another it emis light. | The eye, photocells, Photographic film |
| Ultraviolet | 400 nm to 1 nm | The electrons in inner shell moving from higher energy level to lower eneergy level. | Photocells photographic film |
| X-rays | 1nm to 10-3 nm | Inner shell electrons or X-ray tubes | Geiger tubes, Ionisation chamber,Photographic film |
| Gamma Rays | く10-3 nm | Radioactive decay of the nucleus | Observing the effect gamma-ray on the matter |
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