English: Diffraction pattern of a household spotlight over a smart phone (HTC M8). The phone has a RGB sub-pixel layout in the horizontal direction, leading to a bright interference in the third pattern from the main reflection in the horizontal direction. The phone has a glassy screen protector, which does not affect the diffraction pattern noticeably. This illustrates that as long as light source is narrow and bright enough, we can see the diffraction pattern. For measurements it is better to have a monochromatic light source.