A class uses a shallow ripple tank or a calibrated wave simulation to investigate a wave model. Available equipment and procedure options: Drive both dippers from one bar and photograph low-amplitude lines on a marked observation line. Design an investigation of how the separation of two linked point dippers affects the spacing of adjacent low-amplitude lines at a fixed distance. Include a reasoned hypothesis, an appropriate range, controls, repeat measurements, a results table or graph, and one specific limitation and safety measure. Do not invent experimental results.

Question

Accepted Answer

Vary the separation of two linked point dippers; measure the spacing of adjacent low-amplitude lines at a fixed distance. Predict Greater source separation should usually produce more closely spaced interference features. Keep frequency, depth, source phase, amplitude and observation distance constant, repeat each setting, and use the evidence to test the prediction. State a testable research question linking the separation of two linked point dippers to the spacing of adjacent low-amplitude lines at a fixed distance, rather than asking vaguely which arrangement is best. A suitable prediction is: Greater source separation should usually produce more closely spaced interference features. Justify that prediction scientifically: The same path difference is reached over a smaller angular change when coherent sources are farther apart. This is a hypothesis to test, not a result that the experiment must produce. Use 2, 3, 4, 5 and 6 cm as the planned independent-variable settings. Measure the response using the supplied equipment: Drive both dippers from one bar and photograph low-amplitude lines on a marked observation line. Record quantities with units before calculating any derived result. Keep frequency, depth, source phase, amplitude and observation distance constant. This isolates the proposed cause; changing these conditions at the same time would allow competing explanations for any difference. Take at least three independent trials at each setting, resetting the apparatus each time. Tabulate the setting, individual responses and mean; plot the mean response against the changed quantity and show the range of repeated values. Evaluate this specific limitation: Independent motors may drift in phase; use mechanically linked dippers. More repeats alone do not necessarily correct a biased method. Protect participants and equipment by this precaution: Keep water away from power supplies and use only teacher-approved low-voltage apparatus.

Separating two coherent sources

What a complete response should do

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