electromagnetic waves 2

electromagnetic waves 2 - Electromagnetic waves Working...

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Electromagnetic waves Working with Maxwell’s equations in free space, i.e. no charges or currents …it can be shown that light consists of oscillating electric and magnetic fields E surface dA = 0 B surface dA = 0 E curve ds = d Φ B dt B curve ds = μ o ε o d Φ E dt . . . . You end up with a wave equation where the speed of the wave depends on two constants of nature: ε o and μ o ε o comes in when we talk about electric fields μ o comes in when we talk about magnetic fields 2 E y x 2 = o μ o 2 E y t 2 2 E y x 2 = 1 c 2 2 E y t 2 c = 1 o o = 3 X 10 8 m / s
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Electromagnetic waves Working with Maxwell’s equations in free space, i.e. no charges or currents …it can be shown that light consists of oscillating electric and magnetic fields E surface dA = 0 B surface dA = 0 E curve ds = d Φ B dt B curve ds = μ o ε o d Φ E dt . . . .
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EM waves What we know Stationary electric charges produce electric fields Electric charges in uniform motion (currents) produce electric and magnetic fields Accelerated electric charges produce electric fields, magnetic fields, and electromagnetic waves
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It was left to Heinrich Hertz to verify EM waves EM waves I hope this is enough to get a unit named after me
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Electromagnetic spectrum All electromagnetic waves travel through vacuum with a speed c (3 X 10 8 m/s) For all EM waves, c= λ f (true for any type of wave) λ = c/f The visible portion of the spectrum forms a tiny portion of the total EM spectrum
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Electromagnetic spectrum and the sun
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Views of Crab Nebula X-ray optical infra-red radio increasing wavelength Increasing wavelength
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Clicker question In an electromagnetic wave, the electric and magnetic fields are oscillating A) perpendicular to each other
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electromagnetic waves 2 - Electromagnetic waves Working...

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