# 8.2.1 Transverse & Longitudinal Waves

### Properties of Transverse & Longitudinal Waves

• In mechanical waves, particles oscillate about fixed points
• The direction of oscillations with regards to the direction of wave travel determine what type of wave it is

#### Transverse waves

• A transverse wave is one where the particles oscillate perpendicular to the direction of the wave travel (and energy transfer)
• Transverse waves show areas of crests (peaks) and troughs

Diagram of a transverse wave

• Examples of transverse waves are:
• Electromagnetic waves e.g. radio, visible light, UV
• Vibrations on a guitar string
• These can be shown on a rope
• Transverse waves can be polarised

#### Longitudinal waves

• A longitudinal wave is one where the particles oscillate parallel to the direction of the wave travel (and energy transfer)
• Longitudinal waves show areas of compressions and rarefactions

Diagram of a longitudinal wave

• Examples of longitudinal waves are:
• Sound waves
• Ultrasound waves
• These can be shown on a slinky spring
• Longitudinal waves cannot be polarised
• You will have learned how to analyse the properties of a wave, such as amplitude and wavelength, in “General Wave Properties”
• The diagram below shows the equivalent of a wavelength on a longitudinal wave

Wavelength shown on a longitudinal wave

#### Exam Tip

The definition of transverse and longitudinal waves are often asked as exam questions, make sure to remember these definitions by heart!

### Graphical Representations of Transverse & Longitudinal Waves

#### Worked Example

The graph shows how the displacement of a particle in a wave varies with time.

Which statement is correct?

A. The wave has an amplitude of 2 cm and could be either transverse or longitudinal.

B. The wave has an amplitude of 2 cm and has a time period of 6 s.

C. The wave has an amplitude of 4 cm and has a time period of 4 s.

D. The wave has an amplitude of 4 cm and must be transverse.

#### Exam Tip

Both transverse and longitudinal waves can look like transverse waves when plotted on a graph – make sure you read the question and look for whether the wave travels parallel (longitudinal) or perpendicular (transverse) to the direction of travel to confirm which type of wave it is.

### Author: Ashika

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.
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