Question

If the ratio of the maximum to minimum intensity in beats is $49$, then the ratio of amplitude of two progressive wave trains is::

• A. $7:1$
• B. $4:3$
• C. $49:1$
• D. $16:9$

Answer 1

The correct option is B $4:3$

$\frac{I_{max}}{I_{min}}=\frac{{(a+b)}^2}{{(a-b)}^2}=49$
$\therefore$ $\frac{a+b}{a-b}=7$
$\Rightarrow$ $7a-7b=a+b$
$\Rightarrow$ $6a=8b$
$\Rightarrow$ $\frac{a}{b}=\frac{8}{6}=\frac{4}{3}$