1. The problem statement, all variables and given/known data Sound waves can be refracted when they travel through balloons filled with different gases. How would the motion of a sound wave be changed if it traveled through a balloon filled with carbon dioxide? BOOK ANSWER "Being more dense than air, the carbon dioxide in the balloon will slow down the sound wave. This will tend to focus the sound together, like a lens. (A balloon filled with hydrogen do the opposite)" INTERNET INFORMATION "Sound waves refract in the same way as light waves. When a sound wave is slowed down it bends towards the normal line and when it speeds up it bends away from the normal line. There is one big difference. Light waves slow down when they enter liquids and solids. Sound waves speed up in liquids and solids. Sound travels well in solids because the particles are close together so vibrations can be easily passed along". MY ANSWER Sound waves in air will travel faster in denser liquids and solids (and gases????). Sound travels well in denser materials because the particles are close together so the longitudinal vibrations can be easily passed along. So when sound waves (in air) enter the denser carbon dioxide filled balloon they will bend away from the normal line and travel faster (with larger wavelengths). I think the book answer is wrong based on the internet information that I have read. Please advise.