How does the wavelength change the amount of refraction?

[Muggo]

Using a green laser instead of a red laser seems to change the way the ray changes during refraction. Why is that so?

 

[Drakkith]

A material's index of refraction is wavelength/frequency dependent and typically increases as the wavelength decreases. Hence why green light is refracted more than red light when passing through something like a prism.

 

[phinds]

Using a green laser instead of a red laser seems to change the way the ray changes during refraction. Why is that so?

Just as an aside, have no you not ever seem a prism in action? It splits a white light beam into a spectrum of colors using exactly the mechanism described by Drakkith, so it's hardly surprising that you are getting the results you are getting.

 

[sophiecentaur]

I could throw the question back to the OP and ask why he would expect the refraction to be the same for all frequencies. The spectrum of visible light covers about an octave of frequencies so it's hardly surprising that a phenomenon which involves 'lag' of waves would be frequency dependent.

 

[boneh3ad]

I feel I should point out that with a prism, this is obvious but it's not a general rule. If the propagation medium is nondispersive, for example, then there's no frequency dependence for the phase velocity and therefore refraction.

 

[sophiecentaur]

If the propagation medium is nondispersive,

That would depend upon the range of frequencies involved. Nothing works the same from DC to daylight.

 

[Dadface]

I feel I should point out that with a prism, this is obvious but it's not a general rule. If the propagation medium is nondispersive, for example, then there's no frequency dependence for the phase velocity and therefore refraction.

The only reason it's obvious with a prism is because of its shape, in other words the shape is such that the separation of the wavelengths can be quite large. The same goes for other shapes such as spheres, eg raindrops forming rainbows, and lenses which suffer from chromatic aberation.
With other shapes, for example a parallel sided glass block, the separation due to dispersion can be so small that it may not be noticeable. But even with normal incidence where the there is no separation there is still dispersion because the different frequencies travel at different speeds.
But and this is the main reason I replied to this, are there any nondispersive media apart from a vacuum?