If Declan stands with his back against a wall and gazes directly upwards along the wall to the ceiling, what shape will the junction of the wall and the ceiling make from his perspective? Respond very briefly.
From Declan's perspective, the junction between the wall and the ceiling will appear as a straight line. This is because the ceiling and the wall form a right angle with each other, and looking straight up from the base of the wall, Declan's line of sight would align with the edge where they meet. As a result, this edge or junction will be seen as a straight line, despite being the meeting point of two perpendicular surfaces.