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a combination of two or more different kinds of matter, each of which keeps its own physical properties.
a mixture in which particles of the two substances are evenly mixed and cannot be easily separated.
a form of energy that you can see, travels in a straight line, and can move through empty space where there is no air.
a lens that is thicker in the middle than at the edges and causes light rays to spread apart.
a lens that is thicker at the edges than in the middle and causes light rays to come together.
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