Introduction to Radio Waves and Radio Engineering

Electromagnetic waves propagate in a vacuum with the speed of light, c = 299,792,458 m/s or about 3 X 108 m/s. The electric and magnetic fields of a plane wave oscillate in phase and are perpendicular to each other and to the direction of propagation. The frequency of oscillation is f, and the wavelength is A = c/f Electromagnetic waves also may be considered to behave like particles of zero rest mass. The radiation consists of quanta, photons that have an energy of W = hf where h = 6.6256 X 10"34 Js is Planck's constant.

There are many sources of electromagnetic radiation. Accelerating charges produce electromagnetic radiation, as when charges decelerating in an electric field produce bremsstrahlung and charges orbiting in a magnetic field produce synchrotron radiation. The random thermal motion ofcharged particles in matter produces thermal radiation. Atoms and molecules emit spectral line radiation as their energy level changes. The radiation generated by oscillators and emitted by antennas is based on high-frequency alternating currents.

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