This is a well known and basic topic that you will be trained on before allowed to enter any physics lab with lasers in it. This can happen around shiny objects

This is a well known and basic topic that you will be trained on before allowed to enter any physics lab with lasers in it. This can happen around shiny objects, windows on streets and pretty much anything that reflects light. "So coherent is laser light that one may observe interference effects even when the path difference between the interfering rays is much greater than 109 wavelengths! ... If two waves are exactly “in phase” as shown in Figure 1a, they will reinforce each other; this is called constructive interference." [0] [0] https://faraday.physics.utoronto.ca/IYearLab/intdif.pdf https://faraday.physics.utoronto.ca/IYearLab/intdif.pdf