1. The problem statement, all variables and given/known data You shine two flashlights on a wall. Why don’t you see an interference pattern? 2. Relevant equations 3. The attempt at a solution Actually, I thought you would have seen an interference pattern but if you don’t then it’s probably because the waves of light of the two flashlights are not interacting with each other. In other words, they are not adding up as constructive interference or cancelling each other out by destructive interference so they must not be in sync and so the waves of both flashlights make it to the wall with no “interruptions”. If the waves of the two flashlights were exactly in sync then I presume you would see an interference pattern on the wall.