A narrow monochromatic beam of light of intensity 1 is incident on a glass plate as shown in figure Another identical glass plate is kept close to the first one and parallel to it. Each glass plate reflects `25%` of the light incident on it and transmits intensities in the interference pattern formed by two beams obtained after one reflection at each plate.

Explanation

`I_(1)=I//4, I_(2)=(9I)/64`
`I_(min)/I_(max)=((sqrt(I_(1))-sqrt(I_(2)))/(sqrt(I_(1))+sqrt(I_(2))))^(2)=((sqrt(I//4)-sqrt((9I)/64))/(sqrt(I//4)+sqrt((9I)/64)))^(2)`
`=((1/2-3/8)/(1/2+3/8))^(2)=((1//8)/(7//8))^(2)=1/49`