Transverse and longitudinal waves

OCR

GCSE

Waves transfer energy and information without the net transfer of matter. Transverse waves feature oscillations perpendicular to the direction of energy propagation, exemplified by electromagnetic radiation and seismic S-waves. Longitudinal waves involve oscillations parallel to energy propagation, forming regions of compression and rarefaction, characteristic of sound waves and seismic P-waves. Candidates must analyze these motions using wavefront diagrams and apply the wave equation to calculate velocity, frequency, and wavelength.

Objectives

Exam Tips

Pitfalls

Key Terms

Mark Points

What You Need to Demonstrate

Key skills and knowledge for this topic

Award 1 mark for defining transverse waves as having oscillations perpendicular (at 90 degrees) to the direction of energy transfer
Award 1 mark for defining longitudinal waves as having oscillations parallel to the direction of energy transfer
Credit identification of wavelength as the distance between two consecutive corresponding points (e.g., peak to peak or compression to compression)
Award 1 mark for correct substitution of frequency and wavelength into v = f λ prior to any rearrangement
Credit responses that identify compressions as regions of high pressure/density and rarefactions as regions of low pressure/density

Marking Points

Key points examiners look for in your answers

Award 1 mark for defining transverse waves as having oscillations perpendicular (at 90 degrees) to the direction of energy transfer
Award 1 mark for defining longitudinal waves as having oscillations parallel to the direction of energy transfer
Credit identification of wavelength as the distance between two consecutive corresponding points (e.g., peak to peak or compression to compression)
Award 1 mark for correct substitution of frequency and wavelength into v = f λ prior to any rearrangement
Credit responses that identify compressions as regions of high pressure/density and rarefactions as regions of low pressure/density

Examiner Tips

Expert advice for maximising your marks

💡Use the mnemonic 'Longitudinal is Along' to recall the parallel relationship between oscillation and energy transfer
💡Always write down the equation, then substitute values, then rearrange; this method secures method marks even if the final calculation is incorrect
💡In 6-mark questions describing wave experiments (PAG P8), explicitly state the measuring instruments used (e.g., strobe light, meter ruler, stopwatch) and how they are used to reduce uncertainty

Common Mistakes

Pitfalls to avoid in your exam answers

Stating that the 'wave moves' perpendicular to vibration, rather than specifying the 'direction of energy transfer' relative to oscillation
Confusing the period with the wavelength when reading from a displacement-time graph instead of a displacement-distance graph
Failing to convert kilohertz (kHz) to Hertz (Hz) or centimeters to meters prior to calculation, leading to power-of-ten errors
Describing water waves as purely transverse (they are often modeled as such, but candidates must be careful not to confuse them with longitudinal sound waves)

Study Guide Available

Comprehensive revision notes & examples

Read Study Guide

Key Terminology

Essential terms to know

Oscillation direction relative to energy transfer

Compressions and rarefactions vs. peaks and troughs

Wave equation application (v = fλ)

Experimental determination of wave speed

Likely Command Words

How questions on this topic are typically asked

Define

Describe

Explain

Calculate

Compare

Practical Links

Related required practicals

•{"code":"PAG P8","title":"Measuring the speed of waves in liquids and solids","relevance":"Determination of frequency and wavelength in ripple tanks and on strings"}

Ready to test yourself?

Practice questions tailored to this topic