In traffic signals color light is used to stop vehicles because it has a wavelength.

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Detailed Solution

Concept: In traffic signals red color light is used to stop vehicles because it has the highest wavelength. As we know that red has a longer wavelength, red lights are used to stop automobiles at traffic signals.
When a color has a longer wavelength that color is less dispersion and hence may be seen from further away. One of the key reasons for its employment as a warning signal is that red light is the least dispersed by air molecules. Scattering is inversely proportional to the fourth power of a color wavelength. As a result, blue scatters the most, whereas red scatters the least, because blue has the shortest wavelength of all visible radiations. As a result, in fog, rain, and other similar situations, red light may travel the greatest distance.
Hence, the answers are red and highest respectively.

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