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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

(a) is scattered the most by smoke or fog

(b) is scattered the least by smoke or fog

(c) is absorbed the most by smoke or fog

(d) moves fastest in air



  • Red light has the longest wavelength and is hence least scattered are air/smoke/fog. 
  • This makes it easier to see danger signs even at a distance. 

rayleigh scattering- danger signs are red in colour-01.jpg

So, the correct answer is (b)

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo