Consider a double-slit experiment with narrow slits, you use a screen placed far from the slits to detect the interference pattern. We now add a material in front of just one of the slits so that the light ray is shifted 180° out of phase just before it enters that slit, while the light going through the other slit continues undisturbed.
a. Sketch this situation and the resulting interference pattern.
b. Describe whether this pattern differs from the pattern you drew in 1c. If so, how? If not, why not?