Does light travel at the same speed at either end of the spectrum?
Dominic - If you have light travelling through a vacuum, yes it it. So if you're looking at starlight, which has been travelling through a vacuum in space, all of the different colours of light in the spectrum of light from that star will have travelled to us at the same speed. But if light is travelling through a medium like air or glass, which presents some resistance to the light, which is to say it refracts the light, it bends the light, then different colours travel at different speeds. That's why prisms split up light into different colours. the light is travelling at different speeds through the prims.