Electromagnetic Waves

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Electromagnetic waves
Electromagnetic (EM) waves are transverse waves composed of a sinusoidal electric field oscillation and a sinusoidal magnetic field oscillation. The magnetic and electric field oscillations are in phase (when one is has a maximum displacement so does the other). The magnetic field oscillates perpendicular (90°) to the electric field oscillation. The magnetic field and electric field both oscillate perpendicular to the direction the wave travels. EM waves do not require a medium to propagate and they carry their own momentum. All EM waves travel at the speed of light in a vacuum.

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Polarisation is a property of EM waves (and all transverse waves) that describes the orientation of the displacement perpendicular to the direction of travel. For an EM wave this orientation is typically discussed in terms of the electric field.

Visualisation of EM wave

electromagnetic waves are formed by vibration of an electric charge

- a slower vibration creates a wave with a longer wavelength and a low energy
- a faster vibration creates a wave with a shorter wavelength and a high energy

eg. radio waves (longer wavelength)
infra-red waves
Visible light waves (ROYGBIV)
Ultra violet waves

  • X-rays
  • Gamma rays (shorter wavelength)

Electromagnetic Spectrum

Gamma rays

Wavelength Range

Gamma Rays have the shortest coil wavelength, below about 10 picometers


The first X-ray! http://upload.wikimedia.org/wikipedia/en/thumb/6/6e/Anna_Berthe_Roentgen.gif/180px-Anna_Berthe_Roentgen.gif

Wavelength Range

X-Rays have a wavelength in the range of 10 to 0.01 nanometers

Ultra violet

Skin Cancer, sun burns

Wavelength Range

Visible light

Wavelength Range


Wavelength Range


Wavelength Range

Radio waves

Wavelength Range