Electromagnetic Oscillations and Waves

Oscillating Circuit

In an LC oscillating circuit, the energies of the electric and magnetic fields keep converting into each other.

• Thomson's formula: T = 2π√(LC).
• Frequency: ν = 1/T.
• If C increases 4 times, T increases 2 times, not 4 times.

The period depends on the square root. If L increases 2 times and C increases 8 times, T increases √16 = 4 times.

Electromagnetic Waves

• The theory was created by Maxwell (1860s).
• Hertz discovered them experimentally (1888).
• The radio was invented by A. Popov (1895).
• The speed of the wave in vacuum is c = 3·10⁸ m/s.
• Wavelength: λ = c/ν = cT.

Scientist	Contribution	Year
Maxwell	theory	1860s
Hertz	experimental discovery	1888
Popov	radio	1895

Examples

• A wave with a frequency of 50 MHz = 5·10⁷ Hz: λ = 3·10⁸/(5·10⁷) = 6 m.
• If λ = 150 m, then ν = 3·10⁸/150 = 2·10⁶ Hz = 2 MHz.

1. Convert the frequency to Hz (MHz = 10⁶ Hz)
2. Write λ = c/ν
3. Write the result in meters