Q: Light waves from two coherent sources having intensity ratio 81: 1 produce interference. Then, the ratio of maximum and minimum in the interference pattern will be

Sol: $\large \frac{I_1}{I_2} = \frac{a_1^2}{a_2^2} = \frac{81}{1} $

$\large \frac{a_1}{a_2} = \frac{9}{1} $

a_{1} = 9 a_{2}

$\large \frac{I_{max}}{I_{min}} = \frac{(a_1 + a_2)^2}{(a_1 – a_2)^2} $

$\large \frac{I_{max}}{I_{min}} = \frac{(9 a_2 + a_2)^2}{(9 a_2 – a_2)^2} $

$\large \frac{I_{max}}{I_{min}} = \frac{100}{64} = \frac{25}{16} $