Polarisation

Q1. Which of the following correctly describes the difference between transverse and longitudinal waves?

Multiple Choice · 1 point

• · Transverse waves require a medium; longitudinal waves do not
• · In transverse waves, displacement is perpendicular to energy propagation; in longitudinal waves, displacement is parallel
• · Longitudinal waves have a higher speed than transverse waves
• · Transverse waves cannot transfer energy

Q2. Which of the following is an example of a longitudinal wave?

Multiple Choice · 1 point

• · Light from a lamp
• · A wave on a stretched string
• · A water ripple on the surface of a pond
• · Sound travelling through air

Q3. All electromagnetic waves travel at the same speed in a vacuum. What is this speed?

Multiple Choice · 1 point

• · 3.00 × 10⁶ m/s
• · 3.00 × 10⁸ m/s
• · 3.00 × 10¹⁰ m/s
• · 3.00 × 10⁵ m/s

Q4. In an electromagnetic wave travelling horizontally, the electric and magnetic fields oscillate in directions that are:

Multiple Choice · 1 point

• · Both parallel to the direction of propagation
• · Perpendicular to each other and perpendicular to the direction of propagation
• · Parallel to each other and perpendicular to the direction of propagation
• · Both parallel to each other and parallel to the direction of propagation

Q5. Why can light be polarised but sound cannot?

Multiple Choice · 1 point

• · Light travels faster than sound
• · Sound has a longer wavelength than light
• · Light is a transverse wave; sound is a longitudinal wave and its oscillations are already confined to one direction
• · Light carries more energy than sound

Q6. Unpolarised light passes through a single Polaroid filter. Which of the following best describes the transmitted light?

Multiple Choice · 1 point

• · The light is completely absorbed
• · The light oscillates in all planes perpendicular to its direction of travel
• · The light oscillates in one plane only and its intensity is reduced
• · The light oscillates in one plane only and its intensity is unchanged

Q7. Polarised light is passed through a second Polaroid filter whose transmission axis is at 90° to the first. What is observed?

Multiple Choice · 1 point

• · The light passes through with the same intensity
• · The light passes through with reduced intensity
• · No light is transmitted
• · The light becomes unpolarised again

Q8. The fact that light can be polarised is evidence that it is which type of wave?

Multiple Choice · 1 point

• · Longitudinal, because it requires oscillations in multiple directions
• · Transverse, because polarisation requires oscillations perpendicular to the direction of propagation
• · Longitudinal, because it can travel through a vacuum
• · Transverse, because it travels at 3.00 × 10⁸ m/s

Q9. A TV aerial is designed to receive horizontally polarised signals. To maximise signal reception, the aerial's receiving elements should be aligned:

Multiple Choice · 1 point

• · Vertically, perpendicular to the signal polarisation
• · At 45° to the ground
• · Horizontally, parallel to the plane of polarisation of the signal
• · In any direction, as polarisation does not affect reception

Q10. Arrange the following wave types in order, from those whose oscillations are always longitudinal to those whose oscillations are always transverse.

Ordering · 2 points

• 1. Sound waves in air (always longitudinal)
• 2. Waves on a stretched string (always transverse)
• 3. Electromagnetic waves (always transverse)

Q11. A ____ wave is one in which the displacement of particles or fields is perpendicular to the direction of energy propagation. This means such waves can be ____. Sound is a ____ wave and therefore cannot be polarised.

Fill In Blanks · 3 points

• · transverse
• · polarised
• · longitudinal
• · refracted
• · diffracted
• · electromagnetic