Study Guide

Waves Introduction

Waves Introduction

The idea of a wave in physics is almost staggeringly broad: ocean swells, earthquakes, x-rays, jazz flute solos—they're all described by the same physical concepts. Waves stretch over a wide variety of topics, both in nature and physics class. Describing waves uses the simple trigonometric functions you tackled in math class (sine and cosine) to talk about all kinds of motion in the world; from pendulums to drum heads. In fact, any time an object oscillates—bounces back and forth a little bit from its equilibrium position, like a plucked guitar string—its motion can usually be described by wave physics.

Regardless of their shape or size or whether they're representing ripples in the earth's crust or ripples in a pond, all waves have certain shared characteristics. A wave's amplitude is a measure of its size, while frequency tells you how many times per second the oscillation is occurring. Higher frequency sound waves sound higher (a piccolo makes sound at a much higher frequency than a tuba), while higher frequency light waves look more blue than red.

Waves can interfere with each other, building up or masking over one another. Imagine digging a giant hole in the sand at the beach and piling up all the sand you've excavated next to it; someone else shows up with a pile of sand exactly the same size as what you dug out of your hole. They can either dump their sand into your hole, canceling it out entirely, or dump it on top of the pile of sand you dug out to make the hole, doubling the pile's size.

Finally, all waves have a source, whether that source is a bass drum (low-frequency sound waves) or the sun (lots of light waves and UV radiation). The behavior of the wave can change if the source moves—something called the Doppler Effect.

So break out the surfboards. This chapter will have you waving better than a British monarch on a Beach Boys binge.

Waves Resources

Games and Tools

I've Got the Wave on a String
Make any frequency or amplitude traveling wave on a string, and even play around with damping. Better than jumping rope, but you might burn fewer calories.

Never Let Your Schooling Interfere with Your Education
But educate yourselves on how waves interfere with each other—light, sound, and ripples.

The Science of Hot Pockets
How microwaves heat food and drink.

Videos

Sonic the Wedge Fog
Plane traveling at supersonic speeds will often cause moisture to condense around them in wedge-shaped contrails that precede sonic booms, leaving the traditional Doppler Effect far behind.

Sound Constellations
Some of the people most in tune with wave interference are concert hall architects—who must make sure the performers sound phenomenal from every single seat.

Big Wave Surfing
Most waves we've talked about have small amplitudes, but they do get bigger. Much bigger.

Websites

The Electromagnetic Spectrum, Mostly
If you've ever wondered where Superman's heat vision falls on the spectrum of electromagnetic waves, well, Randall Munroe's got you covered.

Wave Speed Test
Another wave propagation comparison from xkcd—when does Twitter let you know about an earthquake before the earthquake itself?

Shake, Rattle, and Roll
How seismic waves fit into our transverse/longitudinal discussion.

Wave Glider
This unmanned robot uses two very different kinds of waves for power—sunlight and ocean swells.