Question

In which case a light ray does not deviate at the interface of the two media

Answer 1

There is only one condition when a ray of light entering a medium from a different medium will not deviate, when the ray is incident on the interface separating the two medium normally to the interface ie when the angle of incidence is zero. In this case there is no deviation from the original path. If angle of incidence is zero, then the angle of refraction is also zero.