Waves · Quick Reference

Wave Motion Cheat Sheet

Waves · Lesson 1/7

In one line: a wave carries energy from one place to another without transporting matter along with it — from ripples on a pond to sound and light, waves are one of nature's most universal patterns.

Key Ideas

1What is a Wave?. A disturbance that transfers energy through a medium (or through space) without the medium itself moving along with the wave.

2Transverse vs. Longitudinal Waves. In a transverse wave, particles vibrate perpendicular to the wave's direction of travel (like light or a wave on a string). In a longitudinal wave, particles vibrate parallel to the direction of travel (like sound).

3Wavelength, Amplitude, Frequency, and Period. Wavelength (lambda) is the distance between successive identical points (like crest to crest). Amplitude is the maximum displacement from equilibrium. Frequency (f) is cycles per second. Period (T) is time per cycle, T=1/f.

4The Wave Speed Equation. v = f*lambda -- wave speed equals frequency times wavelength, connecting how fast a wave travels to its frequency and spatial spacing.

5Mechanical vs. Electromagnetic Waves. Mechanical waves (like sound or water waves) require a medium to travel through; electromagnetic waves (like light) can travel through the vacuum of space.

Worked Examples

A wave has frequency 5 Hz and wavelength 2m. Find its speed.

10 m/s

A wave travels at 340 m/s with wavelength 0.5m. Find its frequency.

680 Hz

Is a sound wave transverse or longitudinal?

Longitudinal

Formulas

v = f * lambda

T = 1/f

Practice Yourself

A wave has f=10Hz, lambda=3m. Find speed.

30 m/s

A wave travels at 20 m/s with lambda=4m. Find frequency.

5 Hz

Is a wave on a guitar string transverse or longitudinal?

Transverse