At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror. This line is known as a normal line (labeled N in the diagram). The normal line divides the angle between the incident ray and the reflected ray into two equal angles. The angle between the incident ray and the normal is known as the angle of incidence. The angle between the reflected ray and the normal is known as the angle of reflection.
Even if the water were to be cooled from the bottom, the coldest water would float to the top and when the whole pond became 0Â°C the ice would float to the top as it formed. In some cases where rocks are below the freezing point (exposed to the air part of the time, ice can form and stick to the rocks under water.
Most people believe water always freezes at exactly 32Â°F or 0Â°C. While it is true that pure water ice always begins to melt at 0Â°C, liquid water-even pure water-does not necessarily freeze at this temperature, and can remain a liquid at much colder temperatures (see the link below). This is called supercooled water.