© William P. Reinhardt.
Photons in a laser are all in the same quantum state. The waves that correspond to individual photons are all in phase and, as we learned in Unit 5, will interfere when diffracted, for example, through a slit. The complicated interference pattern shown here is the result of shining a green laser into a randomly ordered transparent material. Photons interfere constructively and destructively after scattering within the material, resulting in a chaotic-looking pattern of bright and dark spots and lines. (Unit: 6)