Question: An absorbing medium: assume that the world is filled with an isotropic absorbing medium. A good, simple model of such a medium is obtained by considering a line along which radiance travels. If the radiance along the line is N at x, it will be N - (αdx)N at x + dx.
• Write an expression for the radiance transferred from one surface patch to another in the presence of this medium.
• Now qualitatively describe the distribution of light in a room filled with this medium, for α small and large positive numbers. The room is a cube, and the light is a single small patch in the center of the ceiling. Keep in mind that if α is large and positive, very little light will actually reach the walls of the room.