Longitudinal and transverse

• What is a longitudinal wave

  A wave in which the oscillations of the particles is parallel to the direction of energy transfer.

  There are rarefactions (areas of low pressure)

  and compressions (ares of high pressure)
• What is a transverse wave. Give some examples

  Waves where the particle oscillations are perpendicular to the direction of energy transfer

  For Example: electromagnetic waves
• How fast do electromagnetic waves travel in a vacuum

  3x10^8 m/s (speed of light)
• True or False? The magnetic field and electric field in a electromagnetic wave are parallel to each other

  False. They are right angled to each other
• what does a polarising filter do?

  Only allows oscillations in one plane
• How is polarisation used as evidence of the nature of transverse waves

  Polarisation can only occur if a wave’s oscillations are perpendicular to its direction of travel (as they are in transverse waves)
• How are polarisers used in antennas

  TV and radio signals are usually plane-polarised by the orientation of the rods on the transmitting aerial, so the receiving aerial must be aligned in the same plane of polarisation to receive the signal at full strength