Question

Let $n_1$ and $n_2$ be the two slightly different frequencies of two sound waves. The time interval between waxing and immediate next waning is ..........

• A. $\frac{1}{n_1-n_2}$
• B. $\frac{2}{n_1-n_2}$
• C. $\frac{n_1-n_2}{2}$
• D. $\frac{1}{{2(n}_1-n_2)}$

Answer 1

Answer: (D)

$\frac{1}{{2(n}_1-n_2)}$

Beat frequency during constructive interference(waxing) is ($n_1-n_2$)

Beat frequency during destructive interference (waning) is ($n_1-n_2$)

The combination of two waves will give beat frequency as $2(n_1-n_2)$

Now ,the number of beats produced per one second is defined as the reciprocal of difference in frequencies two sound waves which produce waxing and waning.

$\therefore$ Time interval between waxing and immediate waning is $=\frac{1}{2(n_1-n_2)}$