Why does not light split into 7 colors like when it is passed through glass?

It does, Refractive index depends on frequency, but with some materials it is a much smaller difference, maybe such that it isn't noticeable in the visible spectrum.

Capuchin, you are forgetting one thing. Refraction only occurs when light passes from one medium into another medium which has a different index of refraction. Therefore, white light traveling through just air (or any single medium) will not separate. Or am I missing the point of your story?

I believe he's asking why it doesn't separate when it passes from air, to glass, to air, that's what I took from "through glass".

It all depends on the angles of the edges, if the glass edges are parallel, when it passes into the glass, all the colours separate slightly, then when it pases back out, the colours are not separate but travelling parallel.

However if you have a triangular prism, then both interfaces refract in the same direction, giving a larger angle of separation for the light, so you see the split colors more easily.

OK. I totally agree with your conclusions based on your assumptions of the question. We just disagree on the question.

Wouldn't it be lovely if people who asked questions stuck around to help with the answer :)