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Engineering Exams RRB-JE JE (Junior Engineer) DMS (Depot Material Superintendent) CS (Chemical Supervisor - Research) MS (Metallurgical Supervisor - Research) General Science 2019 24-May-2019 Paper-1 Shift-2 Medium +1 -0.33 CMA (Chemical and Metallurgical Assistant)
Why is red colour preferred for danger signal lights?
Correct Answer: C. Because red colour light has longest wavelength and least scattered by fog and smoke
Explanation: Red light is preferred for danger signals primarily because it has the longest wavelength in the visible spectrum. According to Rayleigh scattering, the amount of light scattered by particles like fog, smoke, or dust is inversely proportional to the fourth power of its wavelength. Because red has the highest wavelength, it is scattered the least by atmospheric interference, allowing the signal to remain visible from a much greater distance and in poor weather conditions compared to other colors. Additionally, the human eye is highly sensitive to red, and it is internationally recognized and psychologically associated with stop, caution, and urgency.
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