Question

what is the speed of of red light and blue light in glass.?​

Answer 1

Light travels at approximately 300,000 kilometers per second in a vacuum, which has a refractive index of 1.0, but it slows down to 225,000 kilometers per second in water (refractive index of 1.3; see Figure 2) and 200,000 kilometers per second in glass (refractive index of 1.5

Answer 2

Wavelength order of visible light :

Violet < Indigo < Blue < Green < Yellow < Orange < Red

Hence the reason statement is true that red light has a longer wavelength than blue.

Velocity of light (red or blue ) in air        va=c

Refractive index of glass     ng=1.5  

Velocity of light (red or blue) in glass      vg=ngc= constant    (independent of the light)

Hence both red and blue travel with same speed in glass.