Conservation of energy and two-slit interference
Teaching Guidance for 14-16
What happened to the energy?
Wrong Track: OK, so in some places there are dark fringes in the interference pattern. This means that there is no light arriving and so no energy is being shifted. Destructive interference has destroyed some energy.
Right Lines: You're absolutely right! No energy is arriving at those points on the screen where there are dark fringes. But, the dark fringes are compensated for by the bright fringes. No energy is being shifted to the dark fringes but extra energy is being shifted to the bright fringes to compensate.