The wire that carries the current from the power source to the outlet or receptacle is the hot wire. Whenever you see a black wire, you know it is hot. There are other wires that carry current in more complicated circuits, but black are always hot.
Total Internal Reflection and the Critical Angle. If a ray of light is leaving a denser medium, it will bend away from the normal. As can be seen from the above diagram, as the angle of incidence inside the material increases the angle of refraction increases to a point at which it leaves the material at 90Ë.
In both cases the angle of incidence equals the angle of reflection at the point that the light ray strikes the surface. Light is also reflected when it is incident on a surface or interface between two different materials such as the surface between air and water, or glass and water.Each time a ray of light strikes a boundary between two materials-air/glass or glass/water-some of the light is reflected. Light reflected from a metal surface with angle of incidence i equal to the angle of reflection i'. The dashed line (normal) is perpendicular to the surface. Figure. 2 Light reflection from a) smooth surface (specular reflection) and b) rough surface (diffuse reflection).