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# Physics/DISPERSION in a river

Question
I was studying dispersion yesterday and suddenly a question popped up in my mind.
My text book says:"All colours of white light travel at the same speed in vacuum and air only.Dispersion takes place in glass prism and water droplet".
Please tell me if my test is wrong.
The question is:
If colours of white light travels at different speed in any other medium then let's say in water in a river. Will dispersion take place in water then? I mean will they split in water in river?
THANK YOU

> Will dispersion take place in water then?
> I mean will they split in water in river?

Yes, some dispersion will take place in a river.
However, the dispersion level is small, because the angle of refraction of any of the light is small. The refractive index between air and water is not as large as that between air and crystal, and the water is simply flat against the air. Thus, there's not a lot of bending to start with; and thus the SPREAD in the angle of refraction between red light and blue light is almost imperceptible.

Also, since dispersion of sunlight is taking place everywhere on the surface of the river, the different colors of light do not become dominant anywhere -- so you end up with white light everywhere below the surface of the river.

Summing it up, our eyes won't detect any color spread when sunlight comes down on a river.
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