Correct Answer - `1:49`
Each plate reflects 25% and transmits `75^(@)` incident beam has an intensity I. this beam undergoes multiple reflections and refractions. The corresponding intensity after each reflection and refraction (transmission) are shown in figure.
Interference pattern is to take place between rays 1 and 2. `I_(1)=I//4` and `I_(2)=9I//64`
`therefore(I_(min))/(I_(max))=((sqrt(I_(1))-sqrt(I_(2)))/(sqrt(I_(1))+sqrt(I_(2))))^(2)=(1)/(49)`