Question

Two light beams produce interference pattern to give maxima and minima on the screen. If the intensities of the light beams are in the ratio of 9: 4, then the ratio of intensities of maxima and minima is

• A. 3 : 2
• B. 5 : 1
• C. 25 : 1
• D. 9 : 1

Answer 1

Answer: (C)

$\frac{I_1}{I_2}=\frac{a_1^2}{a_2^2}$ $\therefore$ $\sqrt{\frac{9}{4}}=\frac{a_1}{a_2}$ $\Rightarrow$ $\frac{a_1}{a_2}=\frac{3}{2}$ $\therefore$ $\frac{I_{\max }}{I_{\min }}=\frac{{(a_1+a_2)}^2}{{(a_1-a_2)}^2}={\left(\frac{3+2}{3-2}\right)}^2$ or $I_{\max }:I_{\min }=25:1$