Question

Your friend is playing a song on a piano. Whenever your friend hits a certain key, the lamp on the top of the piano rattles. Explain why the lamp rattles.
A. The lamp rattles because of the occurring of interference
B. The lamp rattles because of the occurring of diffraction
C. The lamp rattles because of the occurring of resonance
D. None of the above

Answer 1

Hint: When the frequency of the sound waves generated by the piano key matches the natural frequency of the material from which the piano is made, the piano starts vibrating at a large amplitude causing the top of the piano to rattle. The option which matches this phenomenon will be the correct answer to the question.

Complete answer:
We are given that when certain keys of a piano are hit then the lamp on the top of the piano rattles. This means that the piano vibrates at certain frequencies of sound emitted by the piano.
When the frequency of the sound waves generated by a particular piano key matches the natural frequency of the material from which the piano is made, then the resonance occurs and the piano starts vibrating at a large amplitude which causes the lamp on the top of the piano to rattle.
Resonance can be defined as the phenomenon in which the frequency of certain waves matches the natural frequency of an object and the object starts to vibrate at a very large amplitude.
Based on the above discussion, the lamp rattles because of the resonance between the sound waves generated by the piano and the natural frequency of the material of the piano.

Hence, the correct answer is option C.

Note:
1. In the phenomenon of interference and diffraction, we have coherent waves superimposing on each other but resonance depends on the matching of the frequencies of waves.
2. Resonance occurs only when the two frequencies match and since each piano key produces sound of different frequency, the lamp rattle only when a particular key is pressed on the piano.