Question

Compare the speeds of light of wavelength 4000 Å
(i.e, violet light) and 8000 Å (i.e, red light) in vacuum.

Answer 1

Speed of light is independent of wavelength. It depends on the medium in which light travels. As the medium is vacuum, the velocity of light of any wavelength is $3\times {10}^8$ m/s.
Therefore, the ratio of speed is 1:1