3.6 Polarisation

• What is the definition of a transverse wave?

  Oscillations perpendicular to propagation
• Match the wave type with its example:

  Transverse wave ↔️ EM wave

  Longitudinal wave ↔️ Compression wave
• Sound waves are examples of longitudinal waves.


  True
• In a transverse wave, the direction of oscillation is perpendicular
• What is the definition of a longitudinal wave?

  Oscillations parallel to propagation
• What is the phenomenon of polarisation?

  Oscillations restricted to one plane
• How does polarised light differ from unpolarised light?

  Oscillations in a single plane
• Steps involved in producing polarised light using a polarising filter:

  1️⃣ Unpolarised light passes through the filter

  2️⃣ Light oscillating in the filter's plane is transmitted

  3️⃣ Light oscillating in other planes is blocked

  4️⃣ Polarised light is produced
• Why cannot longitudinal waves be polarised?

  Oscillations are parallel to propagation
• Polarised light has oscillations restricted to a single plane.


  True
• Polarised light oscillates in a single plane.


  True
• Polarising filters block light oscillating in all planes.

  False
• Match the feature with its correct description:

  Plane of Oscillation ↔️ All directions perpendicular to propagation (Unpolarised) ||| Single plane (Polarised)

  Direction of Energy Propagation ↔️ Random (Unpolarised) ||| Consistent (Polarised)
• Polarised sunglasses reduce glare by blocking reflected light.


  True
• Malus' law is used in photography to reduce glare from water surfaces.


  True
• LCD screens use polarised light to control the transmission of light through individual pixels
• What type of light do polarising filters in photography block to reduce glare?

  Light oscillating in certain planes
• What is the role of polarisation in optical fibre communications?

  Maintaining signal polarisation
• In optical fibre communications, polarisation is maintained to improve transmission
• Light waves are examples of transverse waves.


  True
• In a longitudinal wave, the direction of oscillation is parallel
• Only transverse waves can be polarised because their oscillations are perpendicular to the direction of energy propagation.
• Unpolarised light oscillates in all directions perpendicular to the direction of propagation
• What is the function of a polarising filter?

  Produces polarised light
• Passing unpolarised light through a polarising filter aligns the waves, resulting in polarised light oscillating in one plane
• How do polarising filters reduce the intensity of unpolarised light?

  Block oscillations in other planes
• Match the feature with its correct description:

  Plane of Oscillation ↔️ All directions perpendicular to propagation (Unpolarised) ||| Single plane (Polarised)

  Propagation Direction ↔️ Random (Unpolarised) ||| Consistent (Polarised)
• What is the relationship between the transmitted light intensity and the angle between the filter's orientation and the light's original polarisation plane?

  $\cos^{2}(\theta)$
• What does Malus' law describe?

  Light intensity through a polariser
• Match the angle with its effect on light transmission through a polariser:

  \( \theta = 0^\circ \) ↔️ Maximum Transmission

  \( \theta = 90^\circ \) ↔️ Minimum Transmission
• What is the transmitted intensity when the angle between the polarisation direction and the polariser's orientation is \( 90^\circ \)?

  0
• How do polarised sunglasses reduce glare when driving on a sunny day?

  Block glare from reflective surfaces
• Polarised sunglasses block horizontally polarised light to reduce glare
• Match the application with how polarisation is used:

  Photography ↔️ Reducing glare from water or glass

  LCD Displays ↔️ Controlling light flow to produce images
• Unpolarised light oscillates in a single plane.

  False
• Polarised light can be produced from unpolarised light.

  True
• The intensity of transmitted light through a polarising filter is proportional to the cosine squared of the angle between the filter's orientation and the light's polarization plane.


  True
• What happens to the intensity of unpolarised light after passing through a polarising filter aligned with its oscillations?

  No change
• Unpolarised light oscillates in all possible directions perpendicular to the direction of propagation
• When unpolarised light passes through a misaligned polariser, its intensity is significantly reduced