Question

Two beams of light of intensity $I_1$ and $I_2$ interfere to give an interference pattern. If the ratio of maximum intensity to that of minimum intensity is $\frac{25}{9}$ , then $\frac{I_1}{I_2}$ is

• A. $\frac{5}{3}$
• B. $4$
• C. $\frac{81}{625}$
• D. $16$
• E. $\frac{1}{2}$

Answer 1

Answer: (D)

$\frac{I_{\max }}{I_{\min }}=\frac{25}{9}$ Or ${\left(\frac{a_1+a_2}{a_1-a_2}\right)}^2=\frac{25}{9}$ where a denotes amplitude.
Or $\frac{a_1+a_2}{a_1-a_2}=\frac{5}{3}$
Or $\frac{a_1}{a_2}=4$
As, ${(amplitude)}^2\propto intensity$
Hence, $\frac{I_1}{I_2}={\left(\frac{a_1}{a_2}\right)}^2=16$