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TheJeeronian t1_jadembn wrote

When light slows down on an angled surface, it is bent. The more it slows, the more it is bent.

Light of different frequencies moves through glass at different speeds. This means that different colors bend different amounts. If multiple colors are lumped together, then each will bend a different amount, and so they will separate.

Cubes also have angles.

Different shapes and glasses can have different effects. The right shaped "prism" can be a magnifying lens. The photographic effect called "chromatic aberration" comes from the camera lens acting as a prism.

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breckenridgeback t1_jadgg8i wrote

> Cubes also have angles.

An object with parallel sides won't act as a prism, because it puts the rays back in parallel as they exit.

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TheJeeronian t1_jadj47s wrote

Not all of the sides on a cube are parallel. Specifically, any two adjacent sides.

That said, even returning the rays to parallel does not mean recombining them. At the first surface they are given different angles, splitting one beam. Returning this set of beams to parallel just means that the colors do not spread even further once they've left.

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breckenridgeback t1_jadl2xu wrote

> That said, even returning the rays to parallel does not mean recombining them. At the first surface they are given different angles, splitting one beam. Returning this set of beams to parallel just means that the colors do not spread even further once they've left.

This is true, but the effect is pretty small, much narrower than a typical light beam, and dominated by diffraction, so you just get fringes of very slight color.

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