Properties of Waves

Objectives

Lesson outcomes

Describe how waves transfer energy without transferring matter overall.
Label wavelength, frequency, amplitude, crest, trough, wavefront, and wave speed on wave diagrams.
Distinguish between transverse and longitudinal waves and classify common examples.
Use the wave equation to calculate wave speed, frequency, or wavelength.

Syllabus

CIE 0625 syllabus points

6 linked

3.1.1 Know that waves transfer energy without transferring matter
3.1.2 Describe what is meant by wave motion as illustrated by vibrations in ropes and springs, and by experiments using water waves
3.1.3 Describe the features of a wave in terms of wavefront, wavelength, frequency, crest (peak), trough, amplitude and wave speed
3.1.4 Recall and use the equation for wave speed v = fλ
3.1.5 Know that for a transverse wave, the direction of vibration is at right angles to the direction of propagation and understand that electromagnetic radiation, water waves and seismic S-waves (secondary) can be modelled as transverse
3.1.6 Know that for a longitudinal wave, the direction of vibration is parallel to the direction of propagation and understand that sound waves and seismic P-waves (primary) can be modelled as longitudinal

Definitions

Required definitions

Frequency
the number of oscillations per unit time.
Wavelength
the distance between corresponding points on successive waves.
Amplitude
the maximum displacement from the rest position.
Transverse wave
a wave where oscillations are at right angles to the direction of travel.
Longitudinal wave
a wave where oscillations are parallel to the direction of travel.

Lesson Notes

Student guidance and lesson notes

Overview

This lesson establishes the vocabulary for the whole topic. Use visible models such as a rope, slinky, or ripple tank first so you can see that the disturbance moves while the medium only vibrates about a fixed position.

What You Need to Know

Remember that waves transfer energy without any net transfer of matter.
Introduce crest, trough, amplitude, wavelength, frequency, wavefront, and wave speed using clear labelled diagrams.
Contrast transverse motion with longitudinal motion and link each to familiar examples.
Model the wave equation with short substitution questions before asking you to rearrange it.

How to Work Through It

Start with a quick retrieval task on vibrations and oscillations from earlier work, then ask what is moving when a pulse travels along a rope.
Demonstrate transverse and longitudinal motion with a rope and slinky, then build a class glossary from the observations.
Practise labelling wave diagrams and classifying examples such as water waves, sound waves, electromagnetic waves, S-waves, and P-waves.
Finish with wave equation questions that mix direct substitution and simple rearrangement.

Check Your Understanding

Check whether you can explain why a cork on water bobs up and down even though the wave travels across the tank.
Try one hinge question that tests whether you know which quantities change when frequency changes in the same medium.

Common Mistakes

Saying the material travels with the wave. Go back to the rope or slinky model and make them describe particle motion separately from wave motion.
Amplitude and wavelength are commonly confused. Keep both on the same diagram and insist on showing the measurement lines.
Some you classify all visible waves as transverse. Use sound as the counterexample and revisit particle motion.

Next Steps

Set a short glossary and diagram labelling task so the key terms are secure before the next lesson.
Carry forward the idea that wave speed depends on the medium, because that becomes important in refraction and sound.