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Question
In following figure shows A, B , C and D represent test tube each of height 20 cm which are filled with water up to heights of 12 cm, 14 cm, 16cm and 18cm respectively. If a vibrating tuning fork is placed over the mouth if test tube D, a loud sound is heard.
- Describe the observations with the tubes A, B and C when the vibrating tuning fork is placed over the mouth of these tubes.
- Give the reason for your observation in each case.
- State the principle illustrated by the above experiment.
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Solution
- No loud sound is heard with the tubes A and C, but a loud sound is heard with the tube B.
- While tubes A and C do not experience resonance with their air columns, tube B does. The air column length in tube D is 20 – 18 = 2 cm, while in tube B it is 20 – 14 = 6 cm, which is three times the length in tube D. Consequently, the frequency of vibrations in both tubes is identical. Contrarily, air column vibrations in tubes A and C do not have the same frequency as those in tube B.
- Resonance happens when the air column vibration frequency is exactly the same as the tuning fork vibration frequency.
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