Question

One beat means that the intensity of sound should be ___________.
(A) Once maximum
(B) Once minimum
(C) Once maximum and once minimum
(D) Twice maximum and twice minimum

Answer 1

Hint :In order to solve this question, we are going to look at the definition of a beat which tells us the prerequisite for a beat to be formed from the sound waves. After that, it is really simple to answer the variation of the intensity of the sound inside a beat, hence to answer the question.

Complete Step By Step Answer:
One beat is an interference pattern between two sounds of slightly different frequencies, perceived as a periodic variation in volume whose rate is the difference of the two frequencies. As the two sound waves approach unison, the beating slows down and may become so slow that it can be neglected easily.
For the interference pattern to be observed, the waves need to superpose, after the interference pattern has been formed, then, there is a formation of the maxima and the minima like any other interference pattern. At the maxima points, the intensity is the maximum while at the minima points, the intensity is the minimum. Thus for a beat to be formed, it is important that the interference takes place. Thus, we can say that a beat means that the intensity of sound should be minimum at one point and maximum at the other. Thus, option (C) Once maximum and once minimum is correct.

Note :
It is important to note that the knowledge of the formation of beats lets us know that they are formed from the interference,
The interference maxima occurs at the wavelength $ n\lambda $ while the interference minima occurs at the point where the wavelength is $ \left( {n + \dfrac{1}{2}} \right)\lambda $ .