Question

The ratio of amplitudes of two coherent waves in Young's double-slit experiment is $\frac{A_{1}}{A_{2}}=\frac{1}{3}$ . What is the ratio of maximum and minimum intensities of fringes?

Answer 1

$\frac{I_{\max }}{I_{\min }}=\frac{\sqrt{I_1}+{\sqrt{I_2}}^2}{\left(\sqrt{I_1}-\sqrt{I_2}\right)^2}=\frac{A_1+3 A_1}{A_1-3 A_1}$
$\frac{I_{\max }}{I_{\min }}=\frac{A_1+3 A_1}{A_1-3 A_1}=\frac{4}{2}^2=4$