Different types of waves travel at different speeds. For example, sound waves travel more slowly than light waves. Have you ever been in a big empty room, or in a cave, and heard an echo? Echos happen because sound waves take time to travel to the wall and bounce back to your ears. But light is different. Light is much faster than sound. Light is the fastest moving thing in the universe. Because light waves and sound waves travel at different speeds, you can figure out how far you are from a storm by watching for lightning and listening for thunder. Lightning and thunder are actually the same thing! Thunder is just the sound that lightning makes. Because light is so quick, you see the lightning flash first. The sound travels more slowly, so you hear the thunder after. Thunder and lightning represent two kinds of waves: sound and light. How do lightning and thunder illustrate the relationship between light and sound waves?
A Light moves faster than sound, so you hear thunder after you see lightning.
B Sound moves faster than light, so you see lightning after you hear thunder.
C Lightning and thunder are the same, so light and sound waves move together at the same time.
D Sound moves light, so when you hear thunder you know lightning will move toward you.