Solar radiation enters a rectangular (i.e., the walls are perpendicular to the floor) canyon, with northern and southern-facing walls, at noon. The canyon walls are 100m tall and 100m apart from each other. The walls and floor of the canyon have an albedo of 0.4. Consider how an individual solar beam is depleted by multiple reflection within the canyon. This beam enters the canyon at a 45^o angle, strikes the south-facing slope at 70m from the canyon floor, and is reflected at a 90^o angle at each point of contact, before finally leaving the canyon.

Using your computer, or graph paper with a straightedge (i.e., do not draw freehand), draw a diagram showing these exchanges. Calculate the effective albedo within the canyon (aka total canyon K*).