Question

in glass the speed of a red ray is that of a violet ray​

Answer 1

Answer:

As, glass has refractive index(1.52) greater than air(1.00029), phase velocity of light reduces. Now, coming to your question, as violet light has shortest wavelength and red has the largest. So, Phase velocity of red is greater than of violet. Or, we can say, red travel faster than violet light

Answer 2

Answer:

glass has refractive index(1.52) greater than air(1.00029), phase velocity of light reduces. Now, coming to your question, as violet light has shortest wavelength and red has the largest. So, Phase velocity of red is greater than of violet. Or, we can say, red travel faster than violet light