Question

A red light signal is used as a danger signal because

Answer 1

In visible spectrum the red colour has larger wave length.The red colour is least scattered by fog or dust particles.So we can observe read colour easily even in foggy and dusty conditions.

Answer 2

Explanation:

Red colour is always used for danger signals, because as red colour is having the longest wavelength, it is the least scattered. So, this signal can be seen from a very long distance