AQA GCSE Physics (8463), Higher tier · Waves › Waves in air, fluids and solids
Practise Waves for detection and exploration. 14 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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What is ultrasound?
Sound with a frequency above 20 kHz (above the upper limit of human hearing).
For the next pulse, the echo from the submarine returns after 0.26 s. Calculate the vertical distance the submarine has moved between the two pulses.
15 m
Give one property, other than its high frequency, that makes ultrasound suitable for medical scanning rather than X-rays.
It is non-ionising, so it does not damage cells (unlike X-rays).
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
(a) What is ultrasound?[1]
(b) Give two uses of ultrasound.[2]
(c) Earthquakes produce seismic waves called P-waves and S-waves. Which statement is correct? Tick (✓) one box.[1]
P-waves are longitudinal and S-waves are transverse.
P-waves are transverse and S-waves are longitudinal.
P-waves and S-waves are both longitudinal.
P-waves and S-waves are both transverse.
(d) Which type of seismic wave cannot travel through a liquid?[1]
Show the answer and mark scheme
(a)Answer: Sound with a frequency above 20 kHz (above the upper limit of human hearing).
sound with a frequency higher than 20 kHz / above the upper limit of human hearing
(b)Answer: Any two: medical imaging (e.g. pre-natal scans); detecting flaws in metal; echo sounding.
medical imaging, e.g. scanning a fetus
industrial imaging, e.g. detecting cracks / flaws in metal
echo sounding / measuring the depth of water / detecting objects under water
(c)Answer: P-waves are longitudinal and S-waves are transverse.
(d)Answer: S-waves
S-waves
Question 2Medium8 marks
A ship uses echo sounding to measure the depth of the water. A transmitter on the bottom of the ship sends a pulse of high-frequency sound down to the seabed. A detector on the ship records the time taken for the echo to return. The speed of sound in seawater is 1500 m/s.
(a) The echo from the seabed returns 0.84 s after the pulse is sent. Calculate the depth of the water below the ship.[3]
(b) As the ship passes over a shoal of fish, the detector records a second, weaker echo. This echo returns 0.30 s after the pulse is sent. Explain why there is a second echo, and why it arrives before the echo from the seabed.[3]
(c) Calculate the depth of the shoal of fish below the ship.[2]
Show the answer and mark scheme
(a)Answer: 630 m
distance travelled = 1500 × 0.84 = 1260 (m)
(the pulse travels down and back so) divide by 2
630 (m)
(b)Answer: The fish partly reflect the pulse (the rest carries on to the seabed); they are nearer than the seabed so their echo returns sooner.
some of the sound is reflected by the fish / at the boundary between the water and the fish
the rest of the sound is transmitted and continues to the seabed
the fish are closer to the ship than the seabed, so the echo travels a shorter distance
(c)Answer: 225 m
1500 × 0.30 ÷ 2
225 (m)
Question 3Hard6 marks
An earthquake produces P-waves and S-waves that travel through the Earth. Seismometers all over the Earth's surface detect the waves. Seismometers on the opposite side of the Earth from the earthquake detect P-waves but no S-waves. There is also a band of the Earth's surface where seismometers detect neither P-waves nor S-waves.
Explain how observations of P-waves and S-waves provide evidence for the structure and size of the Earth's core.[6]
Show the answer and mark scheme
Answer: Level-of-response answer: S-waves cannot pass through liquid, so the S-wave shadow shows a liquid outer core and its size; refraction of P-waves at the core boundary gives the P-wave shadow zone, locating the boundary.
P-waves are longitudinal; S-waves are transverse
P-waves can travel through solids and liquids; S-waves cannot travel through liquids
no S-waves are detected on the opposite side of the Earth, so part of the core must be liquid (the outer core)
the size of the region with no S-waves (S-wave shadow zone) depends on the size of the liquid core, so it can be used to find the radius of the core
the speed of P-waves changes suddenly at the boundary with the core, so they are refracted
this refraction produces a band with no P-waves (P-wave shadow zone)
the speed of the waves changes gradually with depth, so the waves travel along curved paths
the positions of the shadow zones allow the depth of the core boundary to be calculated
the core cannot be observed directly, so seismic waves provide evidence that could not be obtained in any other way
Marked with levels of response: the full level descriptors are in the app.