Waves in Pipes and String | Organ Pipes Most Important Questions For Board

1. Which organ pipe produces a better quality sound a closed pipe or open pipe?

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      Which organ pipes are more used as musical instruments?

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2. What would be the change in pitch of sound when an open pipe is dipped into a liquid up to its half-length?

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3. The frequency of fundamental note of an open organ pipe is double than for closed pipe of same length, why?

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4. A closed organ pipe and an open organ pipe are tuned to the same fundamental frequency, what is the ratio of the lengths?

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5. What types of waves exist in a tuning fork?

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6. Why is a tuning fork made with two prongs? What happens if one of the prongs be cut off?

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7. Why is loud sound heard at resonance?

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8. Explain why soldiers are ordered to break steps while crossing a bridge.

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9. Glass windows are sometimes broken by an explosion several miles away. Explain

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Sometime, the glasses of the windows of a house are found to be shattered when large sounding bodies like airplane pass near the house. Explain how?

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10. One of the nine jewels of Emperor Akbar, widely known as Tansen, was able to break glass by singing appropriate note. What physical phenomenon could account for this?

ans:    Every substance has its natural frequency of oscillation when it is set into vibrations, including glass. When the sound produced by a person can match the frequency of the glass, the amplitude of vibration of the glass walls will be very high, which brings shear to them. When the amount of shear exceeds the breaking point they crack. Reversed maestro Tansen had voice of such matching frequency and he could utter such frequency for a ling time while singing. This could ensure that the glasses crack. In case of other people, either the frequencies do not match or even if they match, they can not emit that frequency for a long time to significantly amplify the vibrations.

11. What is the relation between displacement nodes and antinodes to the pressure nodes and antinodes?

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12. Compare the notes produced from an open pipe with that from a closed pipe.

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13. Why is the pitch of an organ pipe is higher on a hot day?

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14. Why is end correction necessary for organ pipe?

ans:  End Correction is the adjustment to the length of the organ pipe required due to behavior of molecules at the boundary of the open end. Antinode is defined as that point where the displacement of the particles is maximum and it has to happen at the boundary of the open end if he device has to produce loud sound. But those molecules are slightly attracted by the molecules of the pipe themselves which limit their movement. Only the molecules slightly outside are free and are able to perform full degree of movement, which form the antinodes slightly outside.

This adjustment to the distance between the node and antinode is the end correction.

15. What do you mean by end correction of pipe instruments?

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16. Two organ pipes of same length open at both ends produce sound of different frequencies if their radii are different why?

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17. How does the temperature affect the frequency or pitch of an organ pipe?
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The frequency of an organ pipe changes with temperature. Does it decrease or increase with increase in temperature?

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18. There are many holes in a flute. Explain why?

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19. When water is being filled in a vessel, especially long ones, the sound of water falling goes on changing, why?

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20. A vessel is placed below a water tap. We can estimate the height of water level reached in the vessel simply by listening the sound. How?

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21. A helium inhaled person produces high-pitched sound. Why?

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22. When a person has throat problems, a person's voice changes. Why?

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23. Sometimes the whole bodies of bus or any other vehicle start vibrating strongly why?

ans:  The roads on which vehicles travel is never perfectly smooth. So, when vehicles travel on them, their bodies vibrated with varying frequencies. The different parts of vehicles have their own natural frequency of vibration. If the outer frequency matches their natural, the amplitude of their vibrations increase very much. This can be reduced or prevented by decreasing the speed of vehicles.

24. Explain why guitar is more performable than a sarangi to produce quality musical sound?

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25. When the tension in a given stretched string is increased by four times, by what factor does the velocity of transverse wave in the string change?

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26. What happens to the frequency of transverse vibration of a stretched string if its tension is halved and the area of cross section of the string is doubled?

or, f' = f/2. 

Hence the frequency will be halved.

27. Why does sonometer have holes ?

ans:    Sonometer is a box arrangement whose upper surface can be used to place things which are able to produce sound. This sound is sent below where the air column vibrates to give larger sound. The holes are outlets to the sound produced and they also act as the open end for the standing waves formed there. Going by the number of the holes, the box is an open ended pipe.

28. If the mass stretching the sonometer wire is dipped in water, how is the frequency of wire affected?

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29. A sharp and intense sound is heard when a tuning fork struck against a rubber pad is held over a resonance tube and the length of that air column in the tube is adjusted for particular value. Why?

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30. Despite a reasonably steady hand, a person often spills his coffee when carrying it to his seat. Why?

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A person often spills water from a large vessel when carrying from one place to other, why?

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31. When a certain ship passes by, the waves in a harbor sometimes rise to insanely high levels. Why?

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32. Why are musical instruments first warmed up before performing?

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33. A cylindrical tube opens at both ends has fundamental frequency f in air. The tube is dipped vertically in water so that half of it is in water. What is the fundamental frequency of air column?

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