If you increase the angle of incidence of a ray by 20°, how does this change the angle between the incident and reflected ray?
The Italian villagers in Viganella had mountains on each side of them. They could have put a second mirror on the mountain that shaded them from the sun. Would this have helped as much as the mirror they set up on the opposite mountain?
Large mirrors can be placed on the walls of rooms with small windows. How does this help brighten up the rooms compared to having a plain wall?