The contents of a helium balloon are in what phase?

2. how is heavy water different from normal water

__can be defined as which velocity changes

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line