# What is the physical significance of the Planck's constant?

##### 1 Answer

Planck's constant describes the behaviour of particles and waves on the atomic scale. The idea behind its dicovery, that energy can be expressed in discrete units, or *quantized*, proved fundamental for the development of quantum mechanics.

A glass of water, for example, contains a staggering amount of water molecules; it can be said that the smallest unit of water is a water molecule. Imagine that energy behaves the same way - it comes in "smaller units". Planck's constant links a particle's frequency with its total energy.

Planck introduced the constant in his description of the radiation emitted by a blackbody (a perfect absorber of radiant energy). The constant's significance, in this context, was that radiation (light, for example) is emitted, transmitted, and absorbed in discrete energy packets.

Here's a video on blackbody radiation and Planck's constant: