Question

'Red' is used as a danger signal because _________.
1. blood is red.
2. red light is scattered least by the air molecules
3. red colour is easily available.
4. red colour is soothing for eye

Answer 1

Correct Answer - Option 2 : red light is scattered least by the air molecules

The correct answer is red light is scattered least by the air molecules.

• The dispersion of the light is inversely proportional to the fourth power of its wavelength.
  • Because red light has the largest wavelength of all colours, it is the least dispersed.
• The red colour is always used for danger signals because as the red colour is having the longest wavelength, it is the least scattered.
  • So, this signal can be seen from a very long distance.

• As the full spectrum of visible light travels through a prism, the wavelengths separate into the colours of the rainbow because each colour is a different wavelength.
• Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers.