Polarisation

• What is polarisation in waves?

  Oscillations in one direction perpendicular to wave

  
• In which type of waves does polarisation occur?

  Transverse waves
• Why can only transverse waves be polarised?

  They oscillate in any plane perpendicular
• What happens to vibrations in polarised transverse waves?

  Vibrations are restricted to one direction
• How are vibrations oriented in polarised waves?

  Perpendicular to propagation/energy transfer
• Can longitudinal waves be polarised?

  No, they cannot be polarised
• Why can't longitudinal waves be polarised?

  They oscillate parallel to the direction of travel
• What device can polarise waves?

  A polariser or polarising filter

  
• What does a polarising filter do?

  Allows oscillations in a certain plane

  
• What happens when a polarised wave passes through a perpendicular filter?

  None of the wave will pass through
• How can light be polarised besides using filters?

  Through reflection, refraction, and scattering

  
• What happens to light intensity with two polarising filters?

  • Filter A polarises light in a certain axis
  • Maximum intensity when axes are parallel
  • Intensity changes as filter B rotates
  • Minimum intensity when axes are perpendicular

  
• What occurs when one polariser is rotated 90°?

  The intensity drops to zero

  
• Describe the graph of light intensity with angle for two polarisers.

  • Intensity varies with angle
  • Shows periodic changes
  • Maximum and minimum points based on orientation

  
• What happens to unpolarised electromagnetic waves after passing through a polarising filter?

  Their intensity reduces

  
• How do polaroid sunglasses work?

  • Contain vertically oriented polarising filters
  • Block horizontally polarised light
  • Reduce glare from reflective surfaces

  
• What is the effect of reflected light from a horizontal surface?

  It becomes horizontally polarised
• How do polaroid sunglasses help with glare?

  They eliminate partially-polarised light

  
• How do polaroid cameras utilize polarising filters?

  • Capture intensified color
  • Reduce glare on sunny days
  • Useful for underwater photography

  
• Why is light from underwater objects more intense in photos?

  It is refracted, not reflected
• How are radio and television signals polarised?

  • Broadcast as horizontally or vertically polarised
  • Aerial orientation depends on transmitter
  • Correct positioning is essential for reception

  
• What happens if an aerial is not positioned correctly?

  It won't pick up the TV signal