The maximum displacement of a point on a wave from its equilibrium position.

The distance between adjacent points on a wave that are in phase, such as adjacent crests.

What is a transverse wave?

A wave in which the oscillations are perpendicular to the direction of energy transfer.

What is a longitudinal wave?

A wave in which the oscillations are parallel to the direction of energy transfer.

Describe sound in terms of pressure and molecules.

Compressions (high pressure) and rarefactions (low pressure) travel through the air while molecules oscillate backwards and forwards about fixed positions.

What does a displacement-distance graph of a wave show?

The wavelength (between adjacent crests) and the amplitude.

What does a displacement-time graph of a wave show?

The period (time for one cycle), so f = 1/T, and the amplitude.

What are nodes and antinodes?

Nodes are points of zero displacement on a stationary wave; antinodes are points of maximum amplitude.

Core practical 4: which equipment measures the speed of sound?

A signal generator, loudspeaker, microphone and a two-beam oscilloscope.

Core practical 4: why measure across ten wavelengths?

It gives a smaller percentage uncertainty in the wavelength.

If the frequency of a wave in a given medium doubles, what happens to the wavelength?

It halves, because the speed is constant and v = fλ.

Wave properties and the wave equationEdexcel International A Level Physics: Flashcards

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Define amplitude.

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Define amplitude.: The maximum displacement of a point on a wave from its equilibrium position.
Define wavelength.: The distance between adjacent points on a wave that are in phase, such as adjacent crests.
State the relationship between frequency and period.: f = 1/T.
State the wave equation.: v = fλ.
What is a transverse wave?: A wave in which the oscillations are perpendicular to the direction of energy transfer.
What is a longitudinal wave?: A wave in which the oscillations are parallel to the direction of energy transfer.
Describe sound in terms of pressure and molecules.: Compressions (high pressure) and rarefactions (low pressure) travel through the air while molecules oscillate backwards and forwards about fixed positions.
What does a displacement-distance graph of a wave show?: The wavelength (between adjacent crests) and the amplitude.
What does a displacement-time graph of a wave show?: The period (time for one cycle), so f = 1/T, and the amplitude.
What are nodes and antinodes?: Nodes are points of zero displacement on a stationary wave; antinodes are points of maximum amplitude.
What is the distance between adjacent nodes?: Half a wavelength.
Core practical 4: which equipment measures the speed of sound?: A signal generator, loudspeaker, microphone and a two-beam oscilloscope.
Core practical 4: why measure across ten wavelengths?: It gives a smaller percentage uncertainty in the wavelength.
If the frequency of a wave in a given medium doubles, what happens to the wavelength?: It halves, because the speed is constant and v = fλ.

Exam questions on Wave properties and the wave equation

A loudspeaker emits a continuous note of frequency 680 Hz in air, where the speed of sound is 340 m s⁻¹.
The frequency of the loudspeaker is now doubled. State and explain what happens to the speed and to the wavelength of the sound.2 marks
A ship's echo-sounder transmits pulses of ultrasound of frequency 50 kHz. The wavelength of the ultrasound in sea water is 3.0 cm.
A pulse is transmitted vertically downwards and its echo from the sea bed is received 0.40 s later. Calculate the depth of the sea bed.2 marks
A transverse wave travels along a long stretched string. The wave has amplitude 12 mm, frequency 25 Hz and wavelength 0.80 m. At time t = 0 a point P on the string is at its maximum positive displacement.
Describe what is meant by a transverse wave and how the string moves as the wave passes along it.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).