A vertical screen has two narrow slits separated by distance d. A second screen, parallel to the first, is a distance L away (L>>d) and displays the first minimum of the two slit interference pattern a height h above the horizontal line drawn from the center of the slits to the second screen. What is the smallest angle that the second screen be tilted to make that minimum become a maximum? I think that what they're asking for is what angle do we tilt the screen so that a maximum occurs at height h. In that case, if we were to slant the screen towards the slits, would the angle that the second screen is moved be equal to the angle between the two slits? If that's the case, then do we just solve for dsin(theta) = n*lambda? Or would I need make the distance that these two rays travel equal to 1 wavelength by adding another 1/2 wavelength by slanting the screen?