Electromagnetic Waves

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Chapter 34
Electromagnetic Waves
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Chapter 34
- Maxwells Rainbow

• The Traveling Electromagnetic Wave, Qualitatively

• The Traveling Electromagnetic Wave, Quatitatively

• Energy Transport and the Poynting Vector

• Radiation Pressure

• Polarization

• Polarization by Reflection

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Maxwells Rainbow
A beam of light is a traveling wave of electric
and magnetic fields.
We named the electromagnetic spectrum as
Maxwells Rainbow
The visible light is a branch of the
electromagnetic wave
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The visible region of the spectrum (400-700 nm)
which is the sensitivity mostly to the human eye
is the yellow-green light ( ? 555 nm).
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The Traveling Electromagnetic Wave, Qualitatively
. P
LC oscillator is coupled by a transformer and
transmission line to an antenna (two thin, solid,
conducting rods)
The current i(t), sinusoidally varying current at
ang. frequency , associated with the movement
of charge (q) also varies sinusoidally, in
magnitude and direction, at ang freq .
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Bec the dipole mm varies in magnitude and
direction,
Also, bec the i(t) varies,
Together the changing fields form and emw that
travels away at speed C and with ang freq .
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Note The features of emw.
Thus, the wave is a transverse wave.
2.The electric field is always perpendicular to
the magnetic field.
4.The fields always vary sinusoidally, just like
the transverse waves. Moreover, the fields vary
with the same freq and in phase with each other.
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These two wave components can not exist
independently.
All electromagnetic waves, including visible
light, have the same speed C in vacuum.
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Polarization
(b)
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Polarized Light
emw is emitted by the Sun or a bulb are polarized
randomly ( unpolarized).
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We can transform unpolarized visible light into
polarized light by sending it through a
polarizing sheet.
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Polarization by Reflection
Brewsters angle