How does the direction of vibration differ between transverse and longitudinal waves?

In transverse waves, vibrations are perpendicular (90°) to the direction of energy transfer. In longitudinal waves, vibrations are parallel to the direction of energy transfer.

What is the difference between a compression and a rarefaction?

A compression is a region in a longitudinal wave where particles are closest together (high pressure), while a rarefaction is a region where particles are furthest apart (low pressure).

Why can electromagnetic waves travel through a vacuum while sound waves cannot?

Electromagnetic waves are oscillations of electric and magnetic fields that do not require a medium. Sound waves are mechanical longitudinal waves that require particles to vibrate and collide to transfer energy.

What is a common misconception regarding the movement of matter in a wave?

A common error is believing that the particles of the medium travel from the source to the receiver. In reality, particles only oscillate about a fixed position; only the energy moves across the distance.

What mistake is often made when identifying the wave type of a seismic S-wave?

Students often forget that S-waves (Secondary) are transverse. Because they are transverse, they cannot travel through the liquid outer core of the Earth, unlike longitudinal P-waves.

Why is it incorrect to say that a 'Mexican Wave' in a stadium is a longitudinal wave?

In a Mexican Wave, the people (the medium) move up and down while the wave travels sideways. Since the motion is perpendicular to the wave travel, it is a transverse wave, not longitudinal.

Define the 'crest' and 'trough' of a wave.

The crest is the point of maximum positive displacement from the undisturbed position in a transverse wave. The trough is the point of maximum negative displacement.

What is a mechanical wave?

A mechanical wave is a wave that requires a physical medium (solid, liquid, or gas) to transmit energy through the vibration of particles.

Define 'oscillation' in the context of wave motion.

An oscillation is a repetitive back-and-forth motion about a central equilibrium point, which serves as the source of the wave's energy.

How does a bobbing duck on water demonstrate that waves do not transfer matter?

The duck moves up and down (oscillates) as the wave passes but stays in the same horizontal position. This shows that the water molecules are not moving forward with the wave energy.

Transverse & Longitudinal Waves | OCR GCSE Physics

Transverse & Longitudinal Waves

Summary

Waves are periodic oscillations that transfer energy and information from one location to another without the net transfer of matter. They are categorized into transverse and longitudinal types based on the relationship between the direction of particle vibration and the direction of energy propagation.

1. Definition & Core Concepts

Wave Motion: A wave is a disturbance that propagates through a medium or space, transferring energy through repeated vibrations. While the energy moves forward, the individual particles of the medium return to their original equilibrium positions after the wave passes.
Energy vs. Matter: A fundamental principle of wave physics is that waves transfer energy without transferring matter. For instance, a buoy on the ocean will bob up and down as a wave passes but will not be carried forward by the wave itself.
Oscillations: These are the back-and-forth or up-and-down movements about a fixed central point. The nature of these oscillations determines the classification of the wave.

Diagram of a transverse wave showing vibrations perpendicular to the direction of energy travel.

2. Transverse Waves

Direction of Vibration: In a transverse wave, the oscillations of the particles are perpendicular (at 90 degrees) to the direction in which the energy is traveling. This creates a characteristic 'S' shape or undulating pattern.
Structural Features: The highest point of the wave is known as the crest (or peak), while the lowest point is called the trough. The distance from the equilibrium line to a crest is the amplitude.
Medium Constraints: Mechanical transverse waves, such as seismic S-waves, can only travel through solids because they require a medium with shear strength to support the perpendicular motion. However, electromagnetic waves (like light) are also transverse and can travel through a vacuum.

3. Longitudinal Waves

Direction of Vibration: In a longitudinal wave, the particles of the medium vibrate parallel to the direction of energy transfer. The particles move back and forth along the same line that the wave travels.
Structural Features: These waves consist of compressions, where particles are bunched together (high pressure/density), and rarefactions, where particles are spread apart (low pressure/density).
Medium Versatility: Longitudinal waves can travel through solids, liquids, and gases because they rely on pressure variations. Sound is the most common example of a longitudinal wave.

4. Key Distinctions

5. Exam Strategy & Tips

6. Common Pitfalls & Misconceptions