Ok When we look at diffraction, single or double slit, we can obtain the minima and maxima by determining the path lengths and relating that to the wavelength. The idea here is that 1/2 wavelength path difference or 180 deg phase difference result in minima etc. does the The minima, or dark spots, corresponds to NO light being there or No light being able to be detected. What happens to the energy from the electric and magnetic fields? Consider the Michelson M experiement with beam splitter and perfectly refelcting mirrors. A laser is split into two paths and recombined. Lets say its a perfect plane wave even though we can't make one. When the two paths recombine, and if the system is set up for destructive interference, the net magnetic and electric fields combine to give zero at any point in time (for the outgoing pulse). How does the energy in equal the energy out?