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Electromagnetic Waves. CHARITY I. MULIG. Def’n : EM Wave. Energy-carrying wave emitted by vibrating charges (often electrons) that is composed of oscillating electric and magnetic fields that regenerate one another. . The EM Spectrum.

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## Electromagnetic Waves

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**ElectromagneticWaves**CHARITY I. MULIG**Def’n: EM Wave**• Energy-carrying wave emitted by vibrating charges (often electrons) that is composed of oscillating electric and magnetic fields that regenerate one another.**The EM Spectrum**Range of frequencies over which electromagnetic radiation can be propagated.**Change in frequency of a wave of sound or light due to the**motion of the source or the receiver. • Where • fl is the apparent frequency • f0 is the original frequency • v is the speed of the wave in the medium • v0 is the speed observer relative to the medium; positive if the observer is moving towards the source • vs is the speed of the source relative to the medium; positive if the source is moving away from the observer.**Doppler Effect for EM Waves**Observed Frequency Change in Frequency • vs,r = vs – vris the velocity of the source relative to the receiver; it is positive when the source and the receiver are moving further apart. • λo is the wavelength of the transmitted wave in the reference frame of the source.**Def’n: Polarization**• Aligning of vibrations in a transverse wave, usually by filtering out waves of other directions.**Wavefronts vs. Rays**Huygen’s Principle “The wave fronts of light waves spreading out from a point source can be regarded as the overlapped crests of tiny secondary waves – wave fronts are made up of tinier wave fronts”**Properties of EM Waves**• Reflection • Refraction • Diffraction • Dispersion • Scattering • Interference • Polarization**Types of Reflection**Specular/Regular Diffused/Irregular**The open-mesh parabolic dish is a diffuse reflector for**short-wavelength light but a polished reflector for long-wavelength radio waves.**Law of Reflection**• The incident, reflected and normal ray all lie in the same plane. • The angle of incidence is equal to the angle of reflection.**Fermat’s Principle of Least Time**• Pierre Fermat • Out of all possible paths that light might travel to get from one point to another, it travels the path that requires the shortest time.

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