A physics club investigates a resonance tube, shown in Fig. 1. A phone speaker above the tube plays a steady tone. The lower end of the tube is closed by wa...
Question 1 Report
A physics club investigates a resonance tube, shown in Fig. 1. A phone speaker above the tube plays a steady tone. The lower end of the tube is closed by water, and the club raises the water level until the sound becomes much louder. At this point the air column is vibrating strongly. The students mark the air-column length and repeat the procedure with a different tone. They keep the speaker volume constant. The diagram shows one arrangement that gives a loud sound. The water surface acts as the closed end of the air column.
(a) Describe what is meant by resonance in this investigation. [2]
(b) What happens to the loudness when the air column reaches a resonant length? [1]
(c) Explain why the students keep the speaker volume constant. [2]
(d) Give one variable they should measure accurately. [1]
Answer Details
(a) Resonance occurs when the driving frequency matches a natural frequency of the air column. [1] The air then vibrates with a large amplitude. [1]
(b) The loudness increases, so the sound becomes much louder. [1]
(c) Speaker volume affects the amplitude and loudness. [1] Keeping it constant makes this a fair test of the effect of air-column length. [1]
(d) Measure the length of the air column, or the height of the water surface, accurately. [1]
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