Question

The intensity ratio of two waves is $1:9$ . The ratio of their amplitudes, is

• A. $3:1$
• B. $1:3$
• C. $1:9$
• D. $9:1$

Answer 1

Answer: (B)

Intensity $\propto (\text{ amplitude }{)}^2$
$\therefore \frac{I_1}{I_2}=\frac{a_1^2}{a_2^2}\frac{1}{9}=\frac{a_1^2}{a_2^2}$
$\Rightarrow \frac{a_1}{a_2}=\frac{1}{3}$