Red light is used in traffic signals because it has the longest wavelength among visible colors. According to Rayleigh scattering, the scattering of light by atmospheric particles is inversely proportional to the fourth power of its wavelength. Therefore, red light is scattered the least by fog, rain, and dust, allowing it to travel the farthest distance and be easily seen from a long way off, even in adverse weather conditions. Option A is incorrect because red light has the longest, not the lowest, wavelength.
Red light is used in the traffic signal because:
Asked in APPSC Draughtman 2008 · Topic: Optics (Prisms and Dispersion)
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