Speed of different colours of light in glass.?

Question

Is speed of red light faster or slower than speed of violet light in glass? can anyone post a rough list? I know that speed of red light in glass is either the fastest or slowest and i vaugely remember that it is the slowest. Thanks.

Answer 1

Red light has the minimum frequency and maximum wavelength.
Voilet light is just opposite.

For red light,
frequency = 3.85 × 10^14 Hz
wavelength = 7.6 × 10^(-7) m

Thus speed in vacuum = wavelength × frequency
= 2.9 × 10^8 m/s

For voilet light,
frequency = 7.89 × 10^14 Hz
wavelength = 3.8 × 10^(-7) m

Thus speed in vacuum = wavelength × frequency
= 3 × 10^8 m/s

Same is true for glass. To calculate the speed in glass, you need the regractive index of glass.

Thus speed of voilet light in glass is more than red light.

Answer 2

The higher the R.I. the slower the light travels and the refractive index varies with the wavelength of light. For example in fused quartz light of wavelength 200nm (blue end of the spectrum)the R.I is 1.55, for light wavelength 500nm (towards the red end of the spectrum) the index is 1.46 so the speed of light increases with increasing wavelength.
So red light travels faster than blue.

Answer 3

black sheep is correct.

For common materials, the refractive index is lower for longer wavelengths, so red light would travel faster than violet. (Lower index = faster speed)