TWO WAVES IN PHASE TWO WAVES OUT OF PHASE A个个0000 dim bright Figure 3-2. Interference between light waves. When two light waves combine in phase the amplitude of the resultant wave is larger and the brightness is increased. Two light waves that are out of phase partially cancel each other and produce a wave whose amplitude, and therefore brightness, is decreasedFigure 3-2. Interference between light waves. When two light waves combine in phase, the amplitude of the resultant wave is larger and the brightness is increased. Two light waves that are out of phase partially cancel each other and produce a wave whose amplitude, and therefore brightness, is decreased