we know that energy can neither be created nor can be destroyed.But in a paper microphone the vibrations given in the narrower end of a certain frequency & amplitude increases at the wider end?What is the reason for this change in amplitude?Is there any energy acquired by the vibration?Explain.

Asked by  | 4th Oct, 2013, 10:41: PM

Expert Answer:

A paper microphone can be thought of as a pipe open at both ends. However, this pipe has a narrower end and a wider end.
 
When vibrations of a certain frequency enter through the narrower end, they travel through the microphone and exit out of the wider end. Now, in this motion the frequency does not change.
Hence, the sound does not gain any energy as energy is related to frequency or wavelength. Hence, the conservation of energy law is not violated.
 
Now, the pressure at wider end is lower. This causes increase in amplitude of the vibrations. Thus, the sound heard is loud. The loudness of sound is determined by its amplitude.
 
Hence, there is no energy change in paper microphone. Yet, sound heard is loud due to pressure variations.

Answered by Romal Bhansali | 9th Oct, 2013, 10:22: AM

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