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.
The minimum angle at which total internal reflection occurs is known as the critical angle (for Perspex this is about 43Ë). At any angle greater than the critical angle, total internal reflection occurs and the light ray obeys the normal rules for reflection (i.e. angle of incidence = angle of reflection). 1  Page. 2  1. 3  2.
Almost every object will reflect light in some way. In fact, if an object does not produce its own light it will not be visible if it does not reflect that of other sources. Reflection works by angles. Light shines onto a surface in what is called an incident ray. The angle that this ray strikes the surface of the object is measured by imagining a line coming out from the surface at the point that the light strikes it, at right angles to the object.