Two coherent sources whose intensity ratio is $64: 1$ produce interference fringes. The ratio of intensities…
Two coherent sources whose intensity ratio is $64: 1$ produce interference fringes. The ratio of intensities of maxima and minima is
$9: 7$
$8: 1$
$81: 49$
$81: 7$
Solution
The ratio of intensities of maxima and minima
$\frac{I_{\max }}{I_{\min }}=\frac{\left(\sqrt{I_1}+\sqrt{I_2}\right)^2}{\left(\sqrt{I_1}-\sqrt{I_2}\right)^2}$
$=\frac{(\sqrt{64}+\sqrt{1})^2}{(\sqrt{64}-\sqrt{1})^2}$
$\frac{I_{\max }}{I_{\min }}=\frac{(8+1)^2}{(8-1)^2}=\frac{81}{49}$