Interactions of Light

Light from most sources, such as the Sun or a lamp, travels outward in all directions. Light that travels in all directions is called incoherent light. Light that travels in only one direction is called coherent or polarized light. A special filter can be used to polarize light, which only allows light traveling in one direction to pass through. This is how polarizing sunglasses reduce the amount of light you see on a sunny day. However, two polarizing filters placed at right angles to each other will not let any light to pass through. A laser produces a special kind of polarized light that has high energy.