Light from two source, each of same frequency and travelling in same direction, but with intensity in the ratio` 4 : 1` interfere. Find ratio of maximum to minimum intensity.

Explanation

`I_(max)/I_(min)=((sqrtI_1+sqrtI_2)/(sqrtI_1-sqrtI_2))^2`
`=((sqrt(I_1/I_2)+1)/(sqrt(I_1/I_2)-1))^2=((2+1)/(2-1))^2=9:1`