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22.1 Maxwell’s Equations

1865 – James Maxwell unifies electricity and magnetism and shows that their fields move through space as waves.

He calculated that the EM waves travel at the speed of light so they must be a type of light.

1887 – Heinrich Hertz generates and detect EM waves for the first time

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22.2 Production of Electromagnetic Waves

Energy is stored in E and B

Magnitude of E and B are

At large distances, the waves areplanar or flat.

...ΔtΔE

ΔtΔB

ΔtΔE

r1

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22.2 Production of Electromagnetic Waves

EM waves are transverse Amplitude is perpendicular to wave motion

EM waves travel at c = E/B = 3 x 108 m/s

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22.3 Light and the Electromagnetic Spectrum

Speed = Frequency * Wavelength c = f λ

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22.3 Light and the Electromagnetic Spectrum

5

X-ray Visible

Polarized Radio

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22.6 Momentum Transfer and Radiation Pressure

Remember that

Maxwell showed that where a = 1 to 2

Since and then

ΔtΔp

F

cUa

p

AF

Parea

powerintensity

cIa

P

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22.6 Momentum Transfer and Radiation Pressure

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22.7 Wireless Transmission

Radio and wireless telegraph (1890’s)

The FCC and broadcast “bands”

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22.7 Wireless Transmission

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22.7 Wireless Transmission

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22.7 Wireless Transmission