vel through a vacuum.","order":1},{"id":"762283db-3bc4-4d53-81a1-847e86182ac5","content":"Row C","correct":true,"markscheme":"Correct because seismic S-waves are transverse (so they can be polarised) and mechanical (so they cannot travel through a vacuum).","order":2},{"id":"4e99e7b0-0786-411d-95a8-ba65ba83cefb","content":"Row D","correct":false,"markscheme":"Incorrect because longitudinal waves, such as ultrasound, cannot be polarised.","order":3}],"explanation":null,"firstAttemptFullMarks":null},{"id":"66959036-8a93-4cff-9da4-f97a70f18fe6","revisionId":"8eba60a9-8ba8-481a-8410-63abd8ea91f1","questionNumber":null,"questionType":"LA","specification":"A marine researcher is conducting an experiment to measure the speed of sound in seawater. They use a sonar transducer mounted on the hull of a research vessel to emit a short pulse of high-frequency sound vertically downwards towards a flat, horizontal seabed located at a depth of $120\\text{ m}$, as shown in the diagram.\n\n![Sonar speed of sound measurement setup](https://assets.mathsgenie.co.uk/aqa-qb/cbc8a02a-1b2b-4efc-bf91-842f003eb5fd.png)\n\nThe transducer is connected to an oscilloscope that displays the emitted pulse and the returning echo. To find the speed of sound, the researcher starts a manual digital stopwatch when the pulse is emitted and stops it when the echo is observed on the screen.","difficulty":6,"difficultyBand":"medium","totalMarks":6,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"0edf1ad6-140f-4f59-a717-67e67d630e6e","label":null,"content":"Explain **one** way the researcher could improve their method to obtain a more accurate value for the speed of sound in seawater.","markscheme":"- Suggests using the oscilloscope’s internal time-base or electronic cursors to measure the time interval between the pulse and the echo directly (or using an automatic digital data logger) M1\n- Explains that this completely eliminates human reaction time from the time measurement, significantly reducing the percentage uncertainty A1\n- OR: Suggests repeating the time measurement multiple times at the same location M1\n- Explains that this allows anomalous readings to be identified and a more reliable mean time to be calculated A1\n- OR: Suggests taking measurements at several different known depths (by moving the vessel to different locations) M1\n- Explains that plotting a graph of distance ($2 \\times \\text{depth}$) against time and finding the gradient reduces random error and identifies anomalies A1","marks":6,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"electronic_timing","label":"Use electronic timing","steps":[{"type":"text","order":0,"title":"Spot the limitation","content":"Starting and stopping a manual digital stopwatch depends on the researcher's reaction time. This makes the measured time interval between the emitted pulse and returning echo less precise.","highlights":[{"text":"starts a manual digital stopwatch when the pulse is emitted and stops it when the echo is observed on the screen","location":"specification"}]},{"type":"text","order":1,"title":"Time the echo electronically","content":"Use the oscilloscope's internal time-base or electronic cursors to measure the time interval directly between the displayed emitted pulse and the displayed echo.\n\nThis improvement earns **M1**.","highlights":[{"text":"oscilloscope that displays the emitted pulse and the returning echo","location":"specification"}]},{"type":"text","order":2,"title":"Explain the improvement","content":"The oscilloscope measures the interval electronically, so human reaction time is completely removed. This significantly reduces the percentage uncertainty in the time, giving a more accurate value for the speed of sound.\n\nThis explanation earns **A1**."}]},{"id":"repeat_and_average","label":"Repeat and calculate a mean","steps":[{"type":"text","order":0,"title":"Repeat the timing","content":"At the same location, send several pulses and measure the echo time for ea

	Wave	Nature	Can be polarised?	Can travel through a vacuum?
A	FM radio wave	Transverse	No	Yes
B	Seismic P-wave	Longitudinal	No	Yes
C	Seismic S-wave	Transverse	Yes	No
D	Ultrasound wave	Longitudinal	Yes	No

Wave properties and behaviour

Question 21

Wave properties and behaviour Questions

Wave properties and behaviour

Question 21

Wave properties and behaviour Questions