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    Question

    Red light is used for signals because it has

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    A long wavelength Correct Answer Incorrect Answer
    B high intensity Correct Answer Incorrect Answer
    C high frequency Correct Answer Incorrect Answer
    D low refraction in the medium Correct Answer Incorrect Answer

    Solution

    Red is the international colour of stop signs and stop lights on highways and intersections because it is scattered the least by air molecules. The effect of scattering is inversely related to the fourth power of the wavelength of a colour. Red has the highest wavelengthofallthecoloursandisabletotravel the longest distance through fog, rain, and the alike.

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