Electro-magnetic Waves

Electro-magnetic Waves

All the waves in the electromagnetic spectrum...

  • travel the same speed in a vacuum;
  • can be reflected, refracted, diffracted and polarised;
  • are transverse waves.

It is important that you are able to rememeber the different parts of the electromagnetic spectrum and their properties.

A list of the spectrum is shown below:

Type of ray: Gamma rays: X-rays: Ultraviolet: Visible light:
Production: Emitted during radioactive decay Produced by firing electrons at a metal target Emitted by the Sun Emitted by the Sun
Uses: Medicine in chemotherapy Medicine for looking at bones Tanning Seeing
Hazards: Causes cancer by damaging cells Causes cancer by damaging cells Can cause skin cancer Intense light can damage your sight
Wavelength (m): x10-12 x10-10 x10-8 7 x10-7 to 4x10-7
Frequency (Hz): x1020 x1018 x1015 x1014
Photon Energies (eV): 400 k 4 k 4 0.4
Type of ray: Infra red: Micro-waves: Radio-waves:
Production: Emitted by hot objects Produced by changing currents in a conductor Produced by changing currents in a conductor
Uses: Conventional cooking Microwave cooking and communications Communication and media
Hazards: Can burn Can burn Currently not considered to be hazardous
Wavelength (m): x10-5 x10-3 to x10-2 x 1
Frequency (Hz): x1012 x1010 x108 to x1010
Photon Energies (eV): 40µ 4

All of the waves in the electromagnetic spectrum are oscillating electric and magnetic fields. These fields are perpendicular to each other.

Electro-magnetic Waves

These waves can be produced by oscillating electrons in a conductor which sets up the alternating fields. Likewise, the waves can be detected, as the fields will cause electrons to oscillate in a conductor. This is the basic principle behind the production and transmission of radio waves.

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