Light is incident at an angle `phi`with the normal to a vertical plane containing two narrow slits (S1 and S2) at separation d. The medium to the left of slit plane is air and wavelength of the incident light is `lambda`. The medium to the right of the slit plane has refractive index `mu`. Find all values of angular position `(theta) `of a point P where we will observe constructive interference. Wavelength of incident light is `lambda`.

Answer

`theta=sin^(-1)[(1)/(mud)(nlambda-dsinphi)];[n=0,pm1,pm2..]`