### Introduction

Electromagnetic radiation is an energy wave that is composed of an electric field component and a magnetic field component. The electric and magnetic fields are orthogonal to each other and orthogonal to the direction of propogation of the wave.

Schematic of an electromagnetic wave

The wavelength is the length of one complete oscillation and the frequency is the number of oscillations per second. Electromagnetic waves travel through a vacuum at 2.99792x108 m/s, which is known as the speed of light. The relation between speed of light (c), wavelength (lambda), and frequency (nu) is:
c = lambda * nu

### Wave-particle duality

Electromagnetic radiation shows both wave and particle characteristics depending on how the radiation is observed. Einstein first postulated that the energy of radiation is quantized and that radiation is composed of energy packets that were later named photons. The energy (E) of a photon depends on its frequency (or wavelength):

E = h * nu = h * c / lambda

where h is Planck's constant (6.62618x10-34 Js), nu is the frequency of the radiation (Hz), c is the speed of light (2.99792x108 m/s), and lambda is wavelength (m).

### de Broglie equation

Analogous to radiation, particles; such as electrons, protons, and neutrons have wave properties as determined by the de Broglie equation:

lambda = h/p

where lambda is wavelength, h is Planck's constant, and p is the momentum of the particle.

### Further Information

`/chem-ed/light/em-rad.htm, updated 11/3/96`