Electromagnetic Waves

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Electromagnetic Waves
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Maxwells Equations

• Maxwells Equations
• Lorentz Force

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Displacement Current

• Flowing current generates a magnetic field, but
  what about inside a capacitor where current
  doesnt flow?

B

• A changing electric field also generates a
  magnetic field.

E
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Wave Propagation in 3-D

• Plane Waves - Crests of the 3 dimensional wave
  lie in a plane. Intensity remains constant.

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Properties of EM Waves

• E B fields satisfy the same wave equation.
• EM waves travel at velocity,
• E B fields are perpendicular to each other and
  to the direction of travel.
• Magnitude of E B fields obey
• EM waves obey the superposition principle.

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Energy in an EM Wave

• Poynting vector - Rate at which energy flows
  through a unit surface perpendicular to the flow.
  (Units, W/m2)
• Wave Intensity

Electric Wave
Magnetic Wave
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Radiation Pressure

• Light has no mass however, it does have
  momentum.
• For complete absorption of light (inelastic
  collision), the pressure is
• For complete reflection of light (elastic
  collision), the pressure is

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Polarization
Electric Wave

• Preferential orientation of the waves electric
  field vectors.

Magnetic Wave
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EM Spectrum

• Radio waves
• Microwaves
• Infrared Light (IR)
• Visible Light
• Ultraviolet Light (UV)
• X-Rays
• Gamma Rays

Decreasing Wavelength
Increasing Frequency
Speed - 3.0 108 m/s