The process where a light wave's direction is changed due to the wave coming into contact with a different medium. In the atmosphere this especially involves particle diffraction of sunlight, diffraction that causes rainbows, cloud colors, and is the reason why the sky is blue and sunsets red.

1,2-Dimethylbenzene – A colorless liquid with a sweet odor that is classified as a volatile organic compound (VOC) found largely in the atmosphere in high-traffic urban areas 1,2-dimethylbenzene is primarily emitted into the atmosphere through exhaust and emissions from gasoline engines along with industrial emissions from processes such as coal distillation and petroleum refining. This compound is a threat not only in the atmosphere but also to water quality and land surfaces. High concentrations of 1,2-dimethylbenzene in the atmosphere can lead to irritation of the eyes, nose, throat, and can also cause severe breathing problems.