3.1.2 Longitudinal and Transverse Waves

Transverse Waves

• In a transverse wave, the oscillation of particles (or fields) occurs at right angles to the direction of energy transfer. This perpendicular movement is characteristic of transverse waves.

Longitudinal Waves

• In a longitudinal wave, the oscillation of particles occurs parallel to the direction of energy transfer. This results in areas of compression (where particles are close together) and rarefaction (where particles are spread out).

Polarisation of Waves

• Polarisation restricts the oscillations of a wave to a single plane (e.g., only up and down). This process can only apply to transverse waves, as it requires oscillations perpendicular to the direction of wave travel. Longitudinal waves cannot be polarised because their oscillations are already aligned with the direction of travel.
• Significance of Polarisation: The fact that only transverse waves can be polarised provides evidence for the nature of transverse waves. Polarisation shows that transverse waves have oscillations perpendicular to their direction of travel.

Applications of Polarisation

1. Polaroid Sunglasses:

• These sunglasses use polarisation to reduce glare from reflective surfaces (like water and roads). They block light oscillating in certain directions, which helps reduce brightness and makes it easier to see in high-glare environments.

2. TV and Radio Signals:

• TV and radio signals are usually plane-polarised. To receive a strong signal, the receiving aerial must be aligned with the orientation of the transmitted signal. Misalignment can reduce the signal strength, so ensuring both are in the same plane allows for optimal signal reception.