Home > Encyclopedia of Science > Quantum Mechanics

• Macroscopic and submicroscopic properties
• Words to Know
• Uncertainty principle
• A new physics

Quantum mechanics is a method of studying the natural world based on the concept that waves of energy also have certain properties normally associated with matter, and that matter sometimes has properties that we usually associate with energy. For example, physicists normally talk about light as if it were some form of wave traveling through space. Many properties of light—such as reflection and refraction—can be understood if we think of light as waves bouncing off an object or passing through the object.

But some optical (light) phenomena cannot be explained by thinking of light as if it traveled in waves. One can only understand these phenomena by...