A-LevelPhysicsSuperposition9702/12 · May/June 2012 · Q301 Mark
A standing sound wave is set up between a loudspeaker and a wall. A microphone is connected to a cathode-ray oscilloscope (c.r.o.) and is moved along a line directly between the loudspeaker and the wall. The amplitude of the trace on the c.r.o. rises to a maximum at a position X, falls to a minimum and then rises once again to a maximum at a position Y. The distance between X and Y is 33 cm. The speed of sound in air is 330 ms⁻¹. Which diagram represents the c.r.o. trace of the sound received at X?
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
ACRO trace showing approximately two cycles of a sine wave within the 1 cm horizontal marker, with a time base of 0.50 ms/cm.
BCRO trace showing one full cycle of a sine wave within the 1 cm horizontal marker, with a time base of 0.50 ms/cm.
CCRO trace showing approximately two cycles of a sine wave within the 1 cm horizontal marker, with a time base of 0.50 ms/cm.
DCRO trace showing approximately four cycles of a sine wave within the 1 cm horizontal marker, with a time base of 0.50 ms/cm.
✓ Correct answer
B: CRO trace showing one full cycle of a sine wave within the 1 cm horizontal marker, with a time base of 0.50 ms/cm.
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