3.1.1Waves

Features of Waves — Cambridge IGCSE Co-ordinated Sciences 0654 - Physics Revision Notes & Topical Questions

5 min read 10 parts Lesson 2 of 21

📚 Cambridge IGCSE Co-ordinated Sciences 0654 - Physics Hub / Topical Revision

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Part 1 of 8Waves and energy transfer

Waves and energy transfer

Waves

Waves disturbances that transfer energy without transferring matter

Oscillation

Oscillation each part of the medium vibrates about a fixed position and only the pattern and energy travel on

Evidence

Evidence a toy duck or cork bobs up and down as ripples pass but does not move along with the wave

Particles and wave

Particles and wave the particles are not the wave, the motion of the wave causes the particles to move

Medium

Medium sound and water waves need a material medium but electromagnetic waves can travel through a vacuum

Part 2 of 8Showing wave motion

Ropes and springs

Ropes and springs vibrations along them show wave motion

Water waves

Water waves a ripple tank shows frequency, wavelength, amplitude and wave speed

Part 3 of 8Wavefronts

Wavefront

Wavefront a line joining points on the wave that are in step, usually crests, drawn from above

Ray

Ray the arrow showing the direction in which the wave moves

Spacing

Spacing the gap between wavefronts is the wavelength
Close wavefronts mean a short wavelength
Far apart wavefronts mean a long wavelength

Part 4 of 8Amplitude, wavelength and frequency

Amplitude A

Amplitude A the maximum displacement of a wave from its undisturbed position, in metres
Measured from the undisturbed position to a peak or trough
Not measured from crest to trough

Wavelength λ

Wavelength λ the distance from one point on the wave to the same point on the next wave, in metres
Transverse waves from peak to peak
Longitudinal waves from the centre of one compression to the next

Frequency f

Frequency f the number of waves passing a point in a second, in hertz (Hz)

Period T

Period T the time for one complete wave to pass a fixed point, and T = 1 ÷ f

Part 5 of 8Crests, troughs and wave speed

Crest

Crest the highest point of a wave above its undisturbed position

Trough

Trough the lowest point of a wave below its undisturbed position

Wave speed

Wave speed the distance travelled by a wave each second, which is the speed at which energy is transferred through a medium

Bigger amplitude

Bigger amplitude carries more energy but does not change frequency or speed in the same medium

Part 6 of 8Reading wave graphs

Reading wave graphs

Displacement–distance graph

Displacement–distance graph a snapshot at one instant
Distance between neighbouring peaks is the wavelength

Displacement–time graph

Displacement–time graph shows one point moving as time passes
Distance between neighbouring peaks is the period

Amplitude

Amplitude the maximum height above the axis in both graphs

Frequency

Frequency from a time graph f = 1 ÷ T, from a distance graph f = v ÷ λ

Comparing waves

Comparing waves larger height means larger amplitude and more crests in the same distance means shorter wavelength

Part 7 of 8Source and medium

Frequency

Frequency set by the source and unchanged when the wave enters another medium

Speed and wavelength

Speed and wavelength depend on the medium

Sound

Sound amplitude controls loudness and frequency controls pitch

Electromagnetic waves

Electromagnetic waves transverse waves that all travel at 3.0 × 10⁸ m/s in a vacuum

Part 8 of 8More from the specification

1Wave Equation

The fundamental relationship relating wave speed, frequency,
and wavelength, expressed by the equation v = f * lambda, valid for transverse and longitudinal waves alike.

2Reflection at a Surface

When wavefronts meet a flat reflective boundary, the angle of incidence equals the angle of reflection relative to the normal, without altering wavelength or wave speed.

3Refraction Across Boundaries

Waves changing medium experience a change in propagation speed and wavelength while frequency remains unchanged,
causing waves entering a denser medium at an angle to bend toward the normal.

4Diffraction and Wavefront Spreading

When waves spread out beyond a narrow gap, semicircular wavefronts are produced if the gap dimensions approximate the wavelength, leaving wavelength and frequency unaffected.

5Diffraction

Spreading of waves through a gap or around an edge

6Reflection

Light bouncing off a surface.

7Refraction

Change in direction of light when it changes speed between media.

8Spread

The extent to which repeated readings differ.

Key terms

Term	Meaning
Amplitude	Maximum displacement from the undisturbed position
Wavelength	Distance from one point on a wave to the same point on the next wave
Frequency	Number of waves passing a point in one second
Period	Time for one complete wave to pass a fixed point
Wavefront	Line joining points of a wave that are in step
Wave speed	Distance travelled by a wave each second

Avoid these mistakes

Saying the medium travels with the wave — the particles only oscillate about fixed positions.

Measuring amplitude from crest to trough — measure from the undisturbed position to a peak or trough.

Reading a displacement–time graph as a distance graph — the gap between peaks is then the period, not the wavelength.

Using L or W for wavelength — the symbol is λ.

Last updated: 20 October 2026