GCSE Physics revision

Properties of waves

Waves in air, fluids and solids

AQA 4.6.1.2

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AQA student objectives

Learning pathway

ALL 🎯

Describe wave motion in terms of their amplitude, wavelength, frequency and period.

MOST 🎯🎯

Apply the scientific explanation of properties of waves to a relevant example.

SOME 🎯🎯🎯

Analyse a new situation involving properties of waves and explain the scientific reasoning.

Revision summary

Read on screen, then print for Cornell-style active revision.

Waves transfer energy from one place to another without transferring any matter.
The energy carried by waves can be interpreted as meaningful information, such as images from light or sound from music.
Waves travel by vibrating or oscillating as they move from one place to another.

A displacement–distance graph shows how far a wave has travelled from the starting point (distance) against how far it has oscillated from the equilibrium position (displacement).
The maximum displacement of a wave from the equilibrium position is called the amplitude.
The distance of one complete oscillation is called the wavelength, which can be measured from crest to crest or trough to trough.
The highest point of a wave is called the crest, and the lowest point is called the trough.

2. Displacement–Distance GraphsAQA

A displacement–distance graph shows how far a wave has travelled from the starting point (distance) against how far it has oscillated from the equilibrium position (displacement).
The maximum displacement of a wave from the equilibrium position is called the amplitude.
The distance of one complete oscillation is called the wavelength, which can be measured from crest to crest or trough to trough.
The highest point of a wave is called the crest, and the lowest point is called the trough.

A displacement–time graph looks similar to a displacement–distance graph, but has time on the x-axis instead of distance.
The length of one complete oscillation on a displacement–time graph is called the time period, measured in seconds.
The time period is the time taken for one complete oscillation of the wave.

3. Displacement–Time Graphs & Time PeriodAQA

A displacement–time graph looks similar to a displacement–distance graph, but has time on the x-axis instead of distance.
The length of one complete oscillation on a displacement–time graph is called the time period, measured in seconds.
The time period is the time taken for one complete oscillation of the wave.

Frequency is the number of complete oscillations per second and is measured in hertz (Hz).
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Frequency and time period are related by the equation f = T , where f is frequency and T is time period.
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For example, a wave with a time period of 0.5 s has a frequency of 0.5 = 2 Hz.
The equation can be rearranged to find time period: T = f1 , so a wave of 4 Hz has a time period of 0.25 s.

4. Frequency and the Time Period EquationAQA

Frequency is the number of complete oscillations per second and is measured in hertz (Hz).
1
Frequency and time period are related by the equation f = T , where f is frequency and T is time period.
1
For example, a wave with a time period of 0.5 s has a frequency of 0.5 = 2 Hz.
The equation can be rearranged to find time period: T = f1 , so a wave of 4 Hz has a time period of 0.25 s.

Wave speed can be calculated using the equation v = f × λ, where v is wave speed in m/s, f is frequency in Hz, and λ is wavelength in metres.
Wavelength must always be converted into metres before substituting into the equation.
For example, a sound wave with a frequency of 400 Hz and a wavelength of 70 cm (0.7 m) has a wave speed of 400 × 0.7 = 280 m/s.

5. Calculating Wave SpeedAQA

Wave speed can be calculated using the equation v = f × λ, where v is wave speed in m/s, f is frequency in Hz, and λ is wavelength in metres.
Wavelength must always be converted into metres before substituting into the equation.
For example, a sound wave with a frequency of 400 Hz and a wavelength of 70 cm (0.7 m) has a wave speed of 400 × 0.7 = 280 m/s.

In transverse waves, the oscillations are perpendicular to the direction of energy transfer.
Examples of transverse waves include all electromagnetic waves (such as light and radio waves), water waves, and waves on strings such as a guitar.
On a diagram, transverse waves appear to vibrate up and down whilst travelling from left to right.

6. Transverse WavesAQA

In transverse waves, the oscillations are perpendicular to the direction of energy transfer.
Examples of transverse waves include all electromagnetic waves (such as light and radio waves), water waves, and waves on strings such as a guitar.
On a diagram, transverse waves appear to vibrate up and down whilst travelling from left to right.

In longitudinal waves, the oscillations are parallel to the direction of energy transfer.
Longitudinal waves create regions of compression (particles closer together) and rarefaction (particles more spread out) as they travel.
Examples of longitudinal waves include sound waves and seismic P-waves.

The relationship between frequency and time period is f = T1 .
The wave speed equation is v = f × λ, linking wave speed, frequency, and wavelength.
Always ensure units are consistent — wavelength in metres, time period in seconds, and frequency in hertz — before performing calculations.