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Electromagnetic Waves

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Sinusoidal Electromagnetic Waves Electromagnetic Waves ... Where in the cavity is the maximum magnitude electric field and magnetic field? Electromagnetic ... – PowerPoint PPT presentation

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Title: Electromagnetic Waves


1
Electromagnetic Waves
Maxwells Equations
2
Sourceless Maxwells Equations
3
A simple Electromagnetic Wave
Pulse E and B constant within a sheet moving
at velocity v
z
... need to verify consistency with Maxwells
Equations
4
Field lines continue forever each field line
which enters (exits) a closed surface must also
enter (exit), so net number of field lines
entering (exiting) a closed surface must be zero.
5
dA
dl
L
v dt
6
dl
L
dA
v dt
7
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8
General relations between (crossed) E and B
fields creating EM waves.
9
?x
10
Classical Wave Equation!
11
Sinusoidal Electromagnetic Waves
12
Energy in an electromagnetic wave
13
Energy in an electromagnetic wave
14
Energy Flow and Harmonic Waves
15
Example A radio station the surface of the earth
emits 50 kW sinusoidal waves. Determine the
intensity, and the Electric and Magnetic field
amplitudes for an orbiting satellite at a
distance of 100 km from the station.
16
Momentum in an electromagnetic wave
17
Example Satellite in previous example has a 2m
diameter antenna. What is the force of the
radiation on the antenna assuming perfect
reflection?
18
Standing Waves Superposition of equal amplitude
traveling waves of opposite directions.
19
Example EM standing waves are set up in a cavity
used for electron spin resonance studies. The
cavity has two parallel conducting plates
separated by 1.50 cm. a) Calculate the longest
wavelength and lowest frequency of EM standing
waves between the walls. b) Where in the cavity
is the maximum magnitude electric field and
magnetic field?
20
Electromagnetic Spectrum (see graphic) in vacuum,
v c 2.99792458x108 m/s ??f v increasing
frequency ltgt decreasing wavelength visible
spectrum 400 nm (violet) to 700 nm (red)
21
Radiation from a Dipole
22
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