Raj is standing behind a wall that is taller than he is. On the other side of the wall stands Devi, who is of the same height as Raj. There is a small hole at eye level that Raj knows about but Devi does not. Can Raj see Devi, and can Devi see Raj? Respond very briefly.
Raj can see Devi through the hole at eye level because the hole provides a direct line of sight to the other side of the wall. Devi, who is unaware of the hole and is the same height as the wall, cannot see Raj because her view is obstructed by the wall. Devi needs to know about the hole and look through it to see Raj, just as Raj can see her by looking through the hole from his side.