The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because, among all other colours, the red light_

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Is scattered the most by smoke or fog

Is scattered the least by smoke or fog.

Is absorbed the most by smoke or fog

Moves fastest in air

answer is B.

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Detailed Solution

The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because, among all other colours, the red light is scattered the least by smoke or fog.
"The amount of scattering of a light wave is inversely proportional to the fourth power of wavelength."
The wavelength of red light has the longest wavelength, so the amount of scattering would be the smallest. That's why red colour lights are used as danger signals installed at the top of the building and in traffic signals. Red light can go up to a larger distance without deviating.

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