Does changing the medium seem to affect the wave's speed? explain.

Yes. For example if one were to direct light waves into a mixture of radioactive matreial there would be a change in the time it gets there to the bottom by it's initial speed only being 2/3 of it original speed with a certain particle actually beating it using it's own speed this being faster than light. Or if I were to keep with the example of light and giving it the idea of being the niebor of a black holes the light would bend so much in a distorted fashion it would Mark the event horizon where gravity becomes it's medium

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