se/physics/edexcel/questions","basePath":"/gcse/physics/edexcel/wave-properties-and-behaviour/questions","formulaUrl":null,"initialIndex":71,"initialQuestionWindow":[{"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 each one.\n\nThis practical change earns **M1**.","highlights":[{"text":"**one** way the researcher could improve their method","location":"specification"}]},{"type":"text","order":1,"title":"Compare and average","content":"Compare the repeated time readings to identify any anomalous value, then investigate or repeat it before calculatin

Wave properties and behaviour

Question 23

Wave properties and behaviour Questions

Wave properties and behaviour

Question 23

Wave properties and behaviour Questions