Question

Danger signals are red ?why?

Answer 1

Red light has a wide wavelength which makes it visible even from a far distance. So red light is used in signals

Answer 2

$\huge\colorbox{yellow}{Answer!}$

According to Rayleigh's law, the intensity of scattered light is inversely proportional to the forth power of wavelength. in the visible spectrum, red colour has the largest wavelength, it is scattered the least. even in foggy conditions, such a signal covers large distances without appreciable loss of intensity due to scattering. therefore, red coloured signals are preferred.

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