Two waves whose intensities are in the ratio 9:1 interfere.find the ratio of the intensities of bright and dark fringes.

Explanation

Let `A_(1)` and `A_(2)` be the amplitudes of two waves of intensities `I_(1) "and " I_(2)` respectively.
Given that `I_(1)/I_(2)=(9)/(1)`
Again `I_(1)/I_(2)=(A_(1)^(2))/(A_(1)^(2))=(9)/(1) " ""or "(A_(1))/(A_(2))=(3)/(1)`
If `A_("max")` and `A_("min")` are the amplitudes of bright and dark bands, then
`A_("max")/(A_("min"))=(A_(1)+A_(2))/(A_(1)-A_(2)) " ""or"" "A_("max")/(A_("min"))=(3+1)/(3-1)=(4)/(2)=(2)/(1)`
`:.I_(max)/(I_("min"))=(A_("max")^(2))/(A_("min")^(2))=(4)/(1)`