OA - incident ray
i is angle of incidence = 45°
Given r2 = 40°
r2 and r2 are alternate interior angles,
∴ ∠r1 = ∠r2 = 40°
So, angle of refraction = 40°
Since, the emergent ray is parallel to the incident ray, the angle of emergent must be equal to angle of incidence,i.e ∠e = ∠ i = 55°