Waves & Sound
From ocean waves to the sound of your voice, waves carry energy through the universe. Learn how vibrations create everything from music to earthquakes.
"A wave is a way for energy to travel from one place to another without the stuff itself moving along. Think of a crowd doing 'the wave' at a stadium — people just stand up and sit down, but the wave travels all the way around!"
A wave is a disturbance that transfers energy from one place to another. The key insight is that the wave moves, but the medium (the stuff the wave travels through) mostly stays in place.
Drop a stone in a pond and watch the ripples spread outward. The water moves up and down, but it doesn't travel outward with the wave — only the energy does. A duck floating on the water bobs up and down but doesn't get pushed to the shore.
Waves have several important properties: wavelength (the distance between wave peaks), frequency (how many waves pass a point per second), amplitude (the height of the wave), and speed (how fast the wave travels).
Sound waves travel about 4 times faster in water than in air. That's why whales can communicate across hundreds of miles of ocean!
"Sound is just air molecules bumping into each other in a chain reaction. When you clap your hands, you squeeze the air molecules together, and that squeeze travels outward like dominoes falling — until it reaches someone's ear and they hear the clap!"
Sound is a longitudinal wave — meaning the air molecules vibrate back and forth in the same direction the wave travels. When a guitar string vibrates, it pushes air molecules together (compression) and pulls them apart (rarefaction), creating a pattern that travels to your ears.
Pitch is determined by frequency: high frequency = high pitch (like a whistle), low frequency = low pitch (like a bass drum). Volume is determined by amplitude: bigger vibrations = louder sound.
Sound needs a medium to travel through — it can't travel through empty space. That's why there's no sound in outer space! In the movie, when spaceships explode with a big boom, that's actually not realistic.
The speed of sound in air is about 343 m/s (767 mph). When a jet breaks the sound barrier, it creates a sonic boom — a shock wave you can actually hear!
"Light is one of the most fascinating things in the universe. It's a wave, but it doesn't need anything to wave in — it can travel through completely empty space. It's an electromagnetic wave, and it travels at the fastest speed possible in the universe."
Light is an electromagnetic wave — it's made of oscillating electric and magnetic fields. Unlike sound, light doesn't need a medium. It travels through the vacuum of space at an incredible 300,000 kilometers per second (186,000 miles per second).
What we call 'visible light' is just a tiny slice of the electromagnetic spectrum. Radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays are all the same kind of wave — just with different frequencies and wavelengths.
The colors we see correspond to different wavelengths: red light has the longest wavelength we can see, and violet has the shortest. When all visible wavelengths combine, we see white light. A prism separates white light into a rainbow because each color bends by a slightly different amount.
Light from the Sun takes about 8 minutes and 20 seconds to reach Earth. So when you look at the Sun (don't stare!), you're actually seeing it as it was 8 minutes ago!
Experiment & Discover
Play with the simulation below to see physics in action!
Wave Generator
Adjust frequency and amplitude to see how waves change shape!
Test Your Understanding
As Feynman said: "If you can't explain it simply, you don't understand it well enough."
When you drop a stone in a pond, the ripples spread outward. What actually moves outward?
Where You'll See This
Physics isn't just in textbooks — it's everywhere around you!
You see lightning before hearing thunder because light travels much faster than sound
Ultrasound uses high-frequency sound waves to create images of babies before they're born
Noise-canceling headphones work by creating waves that are the exact opposite of incoming sound waves
Earthquakes produce seismic waves that travel through the Earth — scientists use these to study Earth's interior