Answer
9. Longitudinal waves move faster in a denser material because the particles in the material are closer together, allowing the wave to propagate more quickly.
10. If light enters a denser medium, it will slow down and bend towards the normal.
11. The seagull will hear the yell first because sound travels faster in water than in air, and the seagull is closest to the source of the sound.
12. A Coke can appears red because it absorbs all colors of light except for red, which is reflected back to our eyes. This is an example of absorption and reflection of electromagnetic waves.
13. A green folder absorbs all colors of light except for green, which is reflected back to our eyes.
14. We can see everything from outside through a window because the glass allows light to pass through via transmission, while also reflecting some light back via reflection.